PEDIATRIC ULTRASOUND : requisites and applications. [2 ed.] 9783030479091, 3030479099

Table of contents :
Preface for the Second Edition
Acknowledgements
Contents
Part I: Basics/Theory/Methods
1: US Physics
1.1 US Waves
1.2 Propagation and Modulation of US
1.2.1 Acoustic Impedance
1.2.2 Impedance Change
1.2.3 Reflection
1.2.4 Absorption
1.2.5 Deflection
1.2.6 Focus
1.2.7 Resolution
1.3 Emission, Transmission, Reception and Amplification
1.3.1 Emission
1.3.2 Transmission
1.3.3 Reception
1.3.4 Amplification
1.4 Signal Processing
1.4.1 Preprocessing
1.4.2 Post-Processing
1.4.3 Time Gain Compensation (TGC)
1.4.4 Sound Energy = Output
1.4.5 Gain
1.4.6 Frame Rate/Persistence
1.5 Components of US Device
1.5.1 Transducers
1.5.2 Other Parts of US Device
1.6 Modern US Techniques
1.6.1 High-Resolution US (HR-US)
1.6.2 Image Compounding
1.6.3 Harmonic Imaging (HI)
1.6.4 Extended Field of View US
1.6.5 US Texture Analysis
1.6.6 Potential Future for Other Modern Paediatric US Applications
2: US Methods, Artefacts, Biologic Effects, Practice
2.1 A (Amplitude)-Mode
2.2 (T)M-Mode (Time-Motion-Mode)
2.3 B (Brightness)-Mode
2.4 Doppler Sonography
2.5 Artefacts
2.5.1 General Remarks
2.5.2 Common Artefacts
2.5.2.1 Side Loop Artefact
2.5.2.2 Bowing Artefact
2.5.2.3 Noise
2.5.2.4 Marginal Shadowing
2.5.2.5 Posterior Enhancement—Increased through Transmission
2.5.2.6 Reverberation Artefact
2.5.2.7 Increment or Slice Thickness/Beam Width Artefact
2.5.2.8 Mirror Image Artefact
2.5.2.9 Shadowing
2.5.2.10 Refraction Artefact
2.5.2.11 Anisotropy
2.6 Biologic Effects
2.6.1 General Remarks
2.6.2 Thermal Effects
2.6.2.1 Tissue Heating
2.6.2.2 Biological Effects, Tissue Heating
2.6.3 Mechanical Effects and Resonance
2.6.3.1 Cavitation
2.6.4 Potential Risks of Diagnostic US
2.6.4.1 Specific Risks
2.6.4.2 Guidelines and Recommendations
2.6.5 Various Methods and Indices that Allow Estimation of Biological Risks
2.6.5.1 Mechanical Index (MI)
2.6.5.2 Thermal Index (TI)
2.6.5.3 Display of Actual Indices
2.7 How to Perform Paediatric US
2.7.1 Requisites
2.7.1.1 Indications
2.7.1.2 Environmental Requisites
2.7.1.3 Specific Needs in Children
2.7.1.4 Specific Needs in Infants and Newborns
2.7.2 Positioning
2.7.3 Device Handling
2.7.3.1 General Remarks
2.7.3.2 Choice of Device and Transducer
2.7.3.3 How to Start Investigation
2.7.4 Transducer Selection
2.7.4.1 General Remarks
2.7.4.2 Neurosonography (See Chap. 8)
2.7.4.3 Small Part and Musculo-Skeletal US (See Respective Chapters)
2.7.4.4 Chest US (See Chap. 12)
2.7.4.5 Abdominal US (See Respective Chapters)
2.7.5 Course of Investigation and Measurements
2.7.5.1 General Remarks
2.7.5.2 Transducer Handling
2.7.5.3 Measurements
2.8 Documentation and Interpretation
2.8.1 Image Documentation
2.8.1.1 Media for Documentation
2.8.2 Report
2.8.2.1 How to Issue a Report
2.8.2.2 Diagnosis
2.8.2.3 Predefined Reports
2.8.2.4 Nomenclature
3: (Color) Doppler US: Theory, Artefacts, Typical Applications in Childhood
3.1 Doppler Sonography
3.1.1 The Doppler Phenomenon
3.1.2 Different Techniques and Applications of Doppler Sonography
3.1.2.1 Continuous Wave Doppler (CW)
3.1.2.2 Pulsed Wave Doppler (PW)
3.1.2.3 Duplex-Doppler Sonography/Spectral Flow Analysis
3.1.2.4 Colour-Coded Doppler Sonography or Colour Doppler Sonography (CDS)
3.1.2.5 Amplitude-Coded Colour Doppler Sonography (aCDS)
3.1.2.6 Other Flow-Sensitive US Techniques
3.1.2.7 Important Parameters and Measurements (Fig. 3.7)
3.2 Artefacts in (Colour) Doppler Sonography
3.2.1 Aliasing
3.2.2 Spectral Broadening
3.2.3 Sample Volume Artefact
3.2.4 Filtering Artefacts
3.2.5 Scaling Problems
3.2.6 Gain-Induced Errors
3.2.7 Angle Correction
3.2.8 Motion Artefact
3.2.9 Twinkling Artefact
3.2.10 Others
3.3 How to Perform (Colour) Doppler Investigations
3.3.1 Limitations
3.3.2 Interpretation
3.4 Three- and Four-Dimensional US (3D-/4DUS)
3.4.1 Physics and Techniques
3.4.2 Typical Paediatric 3DUS Applications
3.4.2.1 Neonatal Neurosonography
3.4.2.2 3DUS of the Kidney
3.4.2.3 Urinary Bladder 3DUS
3.4.2.4 3DUS of the Paediatric (Female) Genitalia
3.4.2.5 Musculoskeletal 3DUS Applications
3.4.2.6 Small Part 3DUS Applications
3.4.2.7 Other Potential 3D-/4DUS Applications
3.4.3 Benefits of 3D-/4DUS
3.4.4 Restrictions of 3D-/4DUS
3.4.5 Potential Future Paediatric 3DUS Applications
4: Contrast-Enhanced US, and Ultrasound Elastography in Childhood
4.1 Contrast-Enhanced Ultrasound (ce-US)
4.1.1 Basics
4.1.2 ce-US Applications-General Remarks
4.1.3 Contrast-Enhanced Voiding Urosonography (ce-VUS)
4.1.4 Other Intracavitary Use of ce-US: Sono-Genitography, Sonographic Pyelography and Many Potential Others
4.1.5 Intravenous ce-US (CEUS)
4.1.5.1 Potential Applications/Indications of CEUS in Neonates, Infants and Children-Summary
4.1.5.2 Dose Recommendations
4.1.6 Future ce-US Potential
4.2 Ultrasound-/Sonoelastography
4.2.1 Methods
4.2.1.1 Strain Elastography
4.2.1.2 Transient Elastography (TE)
4.2.1.3 Shear Wave Elastography (SWE)
4.2.2 Applications
4.2.2.1 Focal Lesions
4.2.2.2 Diffuse Changes
4.2.2.3 Possible Indications—Summary
5: Paediatric Limited Field of View US/Point of Care US (POCUS) and Emergency US: When, How and for What
5.1 Requirements
5.2 Typical Applications
5.3 “FAST” US (Focused Assessment with Sonography for Trauma)
5.4 “(e)RUSH” (Rapid Ultrasound in Shock and Hypoxia)
5.5 Miscellaneous Other Typical POCUS/Sonoscope Applications
5.6 Restrictions, Pitfalls and Risks of Limited Field US
Part II: Diagnostic Flow Charts, Imaging Algorithms, and Graphs
6: Imaging and Imaging Algorithms for Common Queries in Childhood
6.1 Introduction
6.2 How to Approach Common Urogenital Conditions in Childhood
6.2.1 Urinary Tract Infection (UTI)
6.2.2 Foetal and Neonatal Urinary Tract Dilatation
6.2.3 Urinary Tract Dilatation Later in Childhood and Follow-Up of Neonatally Diagnosed PUJO, UVJO, High-Grade VUR, Complicated Duplex Kidney
6.2.3.1 Pelvi-Ureteric Junction Obstruction (PUJO)
6.2.3.2 Uretero-Vesical Junction Obstruction (= UVJO)/“Megaureter” (MU)
6.2.3.3 Gross Vesico-Ureteric Reflux (VUR)
6.2.4 Urolithiasis (and Nephrocalcinosis)
6.2.5 Cystic Kidney Disease (CKD)
6.2.6 Torsion (Ovary, Testis)
6.2.7 Genital Malformations
6.2.8 Renal Hypertension
6.3 US in Other Common Paediatric Abdominal Conditions and Queries
6.3.1 Necrotizing Enterocolitis (NEC)
6.3.2 Vomiting Infants and Children
6.3.3 Acute Abdomen
6.3.4 Acute Appendicitis
6.3.5 Splenomegaly
6.3.6 Cholestasis
6.3.7 Pancreatitis
6.3.8 Biliary Atresia
6.3.9 Abdominal Trauma
6.3.10 Abdominal Tumours
6.4 Miscellaneous Other Common Queries and Assessment for Systemic Conditions
6.4.1 Pneumonia, Pleural Effusion
6.4.2 Enlarged Mediastinum
6.4.3 Painful Hip/Limping Child: Osteomyelitis
6.4.4 US in Systemic and Syndromatous Disease
7: Measurements and Volume Calculations: Basic Considerations, Graphs and Illustrations for Standardisation
7.1 General Considerations
7.2 How to Measure
7.3 Artifacts and Other Aspects that May Impact Measurements
7.3.1 Miscellaneous Other Considerations
Part III: US Investigations of the Various Organs
8: Neurosonography in Neonates, Infants and Children
8.1 Requisites
8.1.1 Equipment and Transducer Needs
8.1.2 Indications for Brain US
8.1.3 How to Investigate
8.2 Normal Findings
8.2.1 Transfontanellar Access
8.2.2 Alternate Access Findings
8.2.3 Colour Doppler Sonography (CDS)
8.2.4 Normal Variances in Preterm Babies
8.2.4.1 Periventricular Echogenicities
8.2.4.2 Ventricular Asymmetry
8.2.4.3 Ventriculomegaly
8.2.4.4 Cisterna Magna
8.2.4.5 Vascular Variations
8.3 Pathologic Findings
8.3.1 Neural Tube Defects
8.3.1.1 Anencephaly
8.3.1.2 Meningomyelocele and Encephalocele
8.3.1.3 Arnold Chiari Malformation
8.3.1.4 Dandy–Walker Malformations/Spectrum
8.3.1.5 Corpus Callosum Malformations
8.3.1.6 Lipoma
8.3.2 Migration and Gyration Alterations and Disturbances
8.3.2.1 Lissencephaly, Pachygyria, Macro- or Polygyria and Colpocephaly
8.3.2.2 Megalencephaly
8.3.2.3 Schizencephaly
8.3.2.4 Holoprosencephaly
Alobar Holoprosencephaly
Semilobar Holoprosencephaly
Lobar Holoprosencephaly
De Morsier Syndrome: Septo-Optic Dysplasia
Agenesis of the Septum Pellucidum
8.3.2.5 Hydranencephaly
8.3.3 Phakomatoses
8.3.4 Cerebral Cysts
8.3.5 Ischemic Encephalopathy
8.3.5.1 Preterm Infant
8.3.5.2 Global or Diffuse Brain Oedema
8.3.5.3 Focal Hypoxemia and Ischemia
8.3.5.4 (C)DS in Brain Hypoxia
8.3.6 Other applications of (C)DS:
8.3.7 Inflammation
8.3.7.1 Prenatal Intrauterine Infections and Residuals
8.3.7.2 Postnatal Inflammation
8.3.8 Dilatation of CSF Spaces: Hydrocephalus
8.3.9 Cerebral Haemorrhage
8.3.9.1 Haemorrhage in Preterm Babies: IVH Grades I–III, PVH (Fig. 8.37)
8.3.9.2 Haemorrhage in Term Infants
8.3.9.3 Role of CDS in Neonatal Haemorrhage
8.3.9.4 Haemorrhage in Infants and Older Children
8.3.10 Tumours and Space-Occupying Lesions
8.3.10.1 Vascular Malformations
8.3.11 Cerebral Calcifications
8.3.11.1 Non-calcifying Vasculopathy (Lenticulostriate Vasculopathy)
8.4 Ultrasound of the Skull
8.4.1 Introduction
8.4.2 Haematoma
8.4.3 Space-Occupying Lesions and Tumours
8.4.4 Skull Fracture
8.5 Additional Imaging
8.5.1 Plain Film
8.5.2 CT
8.5.3 MRI
8.5.4 Catheter Angiography
8.5.5 Additional Supporting Procedures
8.6 Ultrasound of the Eye and the Orbit
8.6.1 Introduction
8.6.2 Normal Findings
8.6.3 Sonographically Depictable Pathology
9: US of the Neonatal Spinal Canal and Cord
9.1 Introduction
9.2 Requisites
9.3 Transducers and Technique
9.4 Indications
9.5 Normal Findings
9.6 Pathologic Findings of the Spinal Cord
9.6.1 Dysraphism
9.6.2 Other Associated Pathology
9.6.3 Other “Occult” Dysraphisms
9.7 Trauma
9.8 Tumours and Miscellaneous Others
9.9 Other Spinal and Vertebral Pathology
9.10 Additional Imaging
9.11 Value of US
10: Ultrasound of the Neck in Childhood
10.1 Indications, Requisites and Techniques
10.1.1 Transducers
10.1.2 Positioning and Handling
10.1.3 Typical Examinations
10.1.3.1 Cervical Lymph Nodes
10.1.3.2 Glands
10.1.3.3 Cervical Arteries
10.1.3.4 Cervical Veins
10.1.3.5 Intervention
10.2 Normal Findings
10.2.1 Lymph Nodes
10.2.2 Cervical Glands
10.2.2.1 Thyroid Gland
10.2.2.2 Parotid, Submandibular and Sublingual Glands
10.2.3 Other Cervical Soft Tissues
10.2.3.1 Muscles
10.2.3.2 Tonsils
10.2.3.3 Tongue
10.2.3.4 Para- and Retropharyngeal Spaces
10.2.3.5 Larynx
10.2.4 Cervical Vessels
10.3 Pathologic Findings
10.3.1 Lymph Nodes
10.3.2 Pathology of Cervical Soft Tissue
10.3.2.1 Malformations
Cervical Cyst
Dermoid Cyst
Duplication Cysts
Thymic Cyst
Cervical Ectopic Thymus
10.3.2.2 Tumours
Haemangioma
Lymphatic Malformation
Other Mesenchymal Tumours
Neuroblastoma, (Ganglio-)Neuroma, Neurofibroma and Other Nerve (Sheath) Tumours
Teratoma
Other Malignant Tumours
Role of US
10.3.2.3 Abscess Formations
10.3.2.4 Traumatic Changes
Haematoma (Including Sternocleidomastoid Muscle “Haematoma”)
10.3.3 Thyroid Gland
10.3.3.1 Cystic Changes
10.3.3.2 Malformations
10.3.3.3 Inflammation
10.3.3.4 Other Conditions
Hypothyroidism/Struma Diffusa/Colloides (Fig. 10.17)
Nodular Goitre
Amyloid Goitre
Adenoma/Carcinoma
10.3.4 Salivary Glands (Parotid, Sublingual, Submandibular Gland)
10.3.4.1 Inflammation
10.3.4.2 Cysts
10.3.4.3 Calcifications/Sialolithiasis
10.3.4.4 Tumours
10.3.5 Cervical Vessels
10.3.5.1 Arteriosclerosis
10.3.5.2 Dissection
10.3.5.3 Stenosis
10.3.5.4 Other Vascular Anomalies
10.3.5.5 Thrombosis and Occlusion
11: Basics of Paediatric Echocardiography
11.1 Introduction
11.2 Equipment Needs and Specific Considerations
11.2.1 Transducers
11.2.2 Standard US Techniques
11.2.3 Patient Position
11.2.4 Sedation
11.3 Standard Planes and Standardised Course of Examination
11.4 Normal 2D Echocardiogram Findings
11.4.1 Parasternal Views
11.4.1.1 Parasternal Long Axis View (Fig. 11.2)
11.4.1.2 Parasternal Short Axis Views (Figs. 11.3 and 11.4)
11.4.1.3 Apical Views
11.4.2 Subcostal Views
11.4.2.1 Sagittal Subcostal View
11.4.2.2 Subcostal Four-Chamber View (Fig. 11.6)
11.4.3 Suprasternal View (Fig. 11.7)
11.5 Other Techniques
11.5.1 M (Motion)-Mode Echocardiography
11.5.2 Doppler Sonography in Echocardiography
11.5.2.1 CDS with 2DUS
11.5.2.2 PW- and CW-Doppler
11.5.2.3 Calculation of Pressure (P) Gradients (P1 Minus P2)
11.5.3 Assessment of LV and RV Function
11.6 Special Echocardiographic Techniques
11.6.1 Transoesophageal Echocardiography (TEE)
11.6.2 Three-/Four-Dimensional (3D/4D) Echocardiography
11.6.3 Tissue Doppler Imaging (TDI)
11.6.4 Contrast-Enhanced US (ce-US/CEUS)
11.7 Normal Values
11.8 Pathologic Findings
11.8.1 Congenital Heart Defects with Left-to-Right Shunt
11.8.1.1 Atrial Septal Defect (ASD)
11.8.1.2 Atrioventricular Septal Defects (AVSD)
11.8.1.3 Ventricular Septal Defects (VSD)
11.8.1.4 Patent Ductus Arteriosus of Botalli (PDA)
11.8.1.5 Persistent Truncus Arteriosus (Truncus Arteriosus Communis)
11.8.2 Obstructions of Left Ventricular Outflow
11.8.2.1 Aortic Valve Stenosis (AS)
11.8.2.2 Subaortic Stenosis (Sub-AS)
11.8.2.3 Supravalvular Aortic Stenosis
11.8.2.4 Aortic Coarctation (CoA)
11.8.2.5 Interrupted Aortic Arch
11.8.3 Obstructions of the Right Ventricular Outflow
11.8.3.1 Isolated Pulmonary Valve Stenosis (PS)
11.8.3.2 Subvalvular Pulmonary Stenosis
11.8.3.3 Supravalvular Pulmonary Stenosis
11.8.3.4 Tetralogy of Fallot (TOF) and Pulmonary Atresia (PA) with VSD
11.8.4 Miscellaneous Congenital Heart Defects
11.8.4.1 Transposition of Great Arteries (TGA)
11.8.4.2 Total Anomalous Pulmonary Venous Return (TAPVR)
11.8.4.3 Univentricular Heart (UVH)
11.8.4.4 Double Outlet Right Ventricle (DORV)
11.8.4.5 Ebstein Anomaly
11.8.4.6 Cor Triatriatum
11.9 Acquired Paediatric Heart Diseases
11.9.1 Cardiomyopathies (CMP)
11.9.1.1 Hypertrophic CMP
11.9.1.2 Hypertrophic Obstructive CMP (HOCMP)
11.9.1.3 Dilated (Congestive) CMP
11.9.1.4 Restrictive CMP
11.9.2 Acute Myocarditis
11.9.3 Acute (Infective) Endocarditis
11.9.4 Pericarditis/Pericardial Effusion
11.9.5 Kawasaki Disease
11.9.6 Intracardiac Thrombi
11.9.7 Cardiac Tumours
11.10 Modern Approaches, Peri-interventional and Postoperatrive Applications
11.11 Complementing Investigations
11.11.1 Cardiac Catheterisation and Angiography
11.11.2 Cardiac MRI and CT
11.12 When to Do What
11.12.1 Imaging in Typical Clinical Scenarios
11.12.1.1 Typical Orientating Examination
11.12.1.2 Typical Clinical Queries
11.12.2 Trauma and Emergency
12: Ultrasound of the Chest
12.1 Requisites
12.1.1 Transducers
12.1.2 Positioning
12.1.3 Indications
12.1.4 How to Perform Chest US
12.2 Normal Findings
12.2.1 Chest Wall
12.2.2 Breast
12.2.3 Pleural Space
12.2.4 Diaphragm
12.2.5 Lung
12.2.6 Mediastinum
12.2.6.1 Anterior Mediastinum/Thymus
12.2.6.2 Middle Mediastinum
12.2.6.3 Posterior Mediastinum
12.2.7 (Colour) Doppler Sonography
12.2.8 Contrast Enhanced US (ce-US)
12.3 Pathology of Chest Wall
12.3.1 Aplasia: Variations of Ribs
12.3.2 Congenital Malformations
12.3.3 Traumatic Changes
12.3.4 Chest Wall Tumours
12.3.4.1 Lymphangioma (Venolymphatic Vascular Malformation)
12.3.4.2 Lipoma
12.3.4.3 Fibroma/Neurofibroma
12.3.4.4 Other Tumours
12.3.5 Breast
12.3.6 Miscellaneous Other Applications
12.3.7 Role of US and Additional Imaging
12.4 Pathology of Pleural Space
12.4.1 Pneumothorax
12.4.2 Pleural Effusion
12.4.2.1 Empyema
12.4.3 Other Pleural Pathology
12.4.3.1 Role of Imaging
12.5 Pathology of Diaphragm
12.5.1 Diaphragmatic Hernia
12.5.2 Diaphragmatic Motion Disturbance
12.5.3 Role and Potential of Imaging
12.6 Lung Pathology
12.6.1 Pneumonia
12.6.2 Lung Abscess
12.6.3 Atelectasis
12.6.4 Respiratory Distress Syndrome (RDS)/Hyaline Membrane Syndrome, Wet lung, Alveolo-interstitial syndrome
12.6.5 Sequestration
12.6.6 Congenital Cystic Adenomatoid Malformation (CCAM)
12.6.7 Cysts
12.6.8 Infarction
12.6.9 Tumours and Space-Occupying Lesions
12.7 Other Miscellaneous and Rare Applications
12.7.1 US for Interstitial Lung Disease/Alveolar-Interstitial Syndrome
12.8 Additional Imaging
13: Upper Abdominal US in Neonates, Infants and Children: (Excluding the Kidneys)
13.1 Introduction
13.2 Requisites and Investigation
13.2.1 Preparation
13.2.2 Positioning
13.2.3 Transducers
13.3 Liver
13.3.1 Course of Investigation
13.3.2 Standard Planes
13.3.3 Normal Findings
13.3.3.1 Structure
13.3.3.2 Ligaments
13.3.3.3 Hepatic Veins (HV)
13.3.3.4 Portal Vein (PV)
13.3.3.5 Hepatic Artery (HA)
13.3.3.6 Gall Bladder
13.3.3.7 Common Bile Duct
13.3.3.8 Intrahepatic Bile Ducts
13.3.3.9 Doppler Findings
13.3.3.10 Special Aspects of Newborns and Infants
13.3.4 Pathology of the Liver
13.3.4.1 Congenital Changes and Normal Variance
Situs Inversus (Abdominalis)
Butterfly or Midline Liver
Hypoplasia/Atrophy of Left Liver Lobe and Other Variations
13.3.4.2 Inflammatory Conditions
Hepatitis
Liver Abscess
Granulomatous Disease
Role of US
13.3.4.3 Other Parenchymal Liver Disease
Hepatopathy
Fatty Liver/Steatosis
Liver Congestion
Liver Fibrosis
Cirrhotic Liver
Liver Involvement in Systemic Disease
Role of US
13.3.4.4 Portal Hypertension and Vascular Problems
Portal Hypertension
Vascular Malformations
Portal Vein and Hepatic Artery Stenosis
Congenital Agenesis or Variants of Portal Vein/Congenital Portocaval Anastomosis/Abernethy Malformations
Hepatic Vein Thrombosis/Occlusion/Stenosis
Portosystemic Shunts
13.3.4.5 Liver Trauma
Liver Haematoma
Contusion
Laceration
Haemobilia
Associated Diaphragmatic Injury
Liver Infarction
Role of US in Liver Trauma
Additional Imaging
13.3.4.6 Space-Occupying Liver Lesions
Simple Cysts
Complicated Cysts
Liver Calcifications
Intrahepatic Gas
Haemangioma
Mesenchymal Hamartoma
Focal Nodular Hyperplasia (FNH)
Hepatic Adenoma
Fatty Tumours
Hepatoblastoma
Hepatocellular Carcinoma
Hepatic Sarcomas
Metastasis
Proliferative Disorders
Role of US
Additional Imaging
13.4 Biliary Tract and Gall Bladder
13.4.1 General Findings
13.4.2 Congenital Conditions and Normal Variants of Biliary Tract
13.4.2.1 Intrahepatic Gall Bladder
13.4.2.2 Hypo-/Aplasia of Gall Bladder/Biliary Atresia/Neonatal Hepatitis Syndrome
13.4.2.3 Choledochal Cyst
13.4.3 Biliary Tract Diseases
13.4.3.1 Aerobilia
13.4.3.2 Cholestatic Changes/Inspissated Bile/Gallstone
13.4.3.3 Sclerosing Cholangitis
13.4.3.4 Other Forms of Cholangitis and Cholecystitis
13.4.3.5 Tumour-like Conditions
Polyps
Tumours
13.4.3.6 Role of US
13.4.3.7 Additional Imaging
13.5 US in Liver Transplantation
13.5.1 Pretransplant US
13.5.1.1 Recipient Evaluation
13.5.1.2 Donor US (Split Liver Transplant, Related Living Donor—Deceased Donor)
13.5.2 Intraoperative US
13.5.3 Postoperative Assessment
13.5.4 Typical Complications
13.6 Spleen
13.6.1 Requisites
13.6.2 Positioning
13.6.3 Indications
13.6.4 Course of Investigation
13.6.5 Normal Anatomy
13.6.6 Normal Variants
13.6.6.1 Splenunculus (Accessory Spleen)
13.6.6.2 Splenic Lobulations and Clefts
13.6.7 Malformations
13.6.7.1 Asplenia
13.6.7.2 Polysplenia Syndrome
13.6.7.3 Wandering Spleen
13.6.8 Splenomegaly
13.6.9 Trauma
13.6.10 Splenic Infarction
13.6.11 Space-Occupying Lesions of the Spleen
13.6.11.1 Cysts
13.6.11.2 Inflammation and Abscess
13.6.11.3 Tumours and Space-Occupying Lesions
13.6.11.4 Role of US
13.7 Pancreas
13.7.1 Requisites
13.7.2 Indication
13.7.3 Course of Investigation
13.7.4 Normal Findings
13.7.5 Variations and Malformations
13.7.5.1 Annular Pancreas
13.7.5.2 Pancreas Divisum
13.7.6 Inflammation: Pancreatitis
13.7.6.1 Oedematous or Reactive Pancreatitis
13.7.6.2 Haemorrhagic or Necrotising Pancreatitis
13.7.6.3 Chronic Pancreatitis
13.7.7 Trauma
13.7.8 Space-Occupying Lesions
13.7.8.1 Cysts/Pseudocysts
13.7.8.2 Tumours
13.7.9 Role of US
13.7.10 Additional Imaging
13.8 Retroperitoneum and Retroperitoneal Structures: Abdominal Vessels and Abdominal Wall
13.8.1 Abdominal Vessels
13.8.1.1 Positioning
13.8.1.2 Transducers
13.8.1.3 How to Investigate
13.8.1.4 US Findings
13.8.1.5 Important Variants and Malformations
13.8.2 Vascular Pathology
13.8.2.1 Thrombosis/Occlusion
13.8.2.2 Pelvic Congestion Syndrome
13.8.2.3 Mid-Aortic Syndrome
13.8.2.4 Retroaortic Left Renal Vein: Nutcracker Syndrome
13.8.2.5 Compression by Superior Mesenteric Artery (Also Called Nutcracker or SMA Syndrome)
13.8.2.6 Arteriosclerotic Changes and Aneurysms
13.8.2.7 Embolic Thrombus to Abdominal Aorta
13.8.2.8 Role of US
13.8.2.9 Complementing Imaging
13.8.3 Retroperitoneal Soft Tissues
13.8.3.1 Lymph Nodes
13.8.3.2 Retroperitoneal Tumours
13.8.3.3 Abdominal Wall
14: US of the Gastrointestinal (GI) Tract
14.1 Stomach
14.1.1 Requisites
14.1.2 How to Investigate
14.1.2.1 Access
14.1.2.2 Functional Assessment of Bowel and Stomach
14.1.3 Normal Findings
14.1.4 Normal Variants
14.1.5 Malformations
14.1.5.1 Microgastria
14.1.5.2 Pyloric Atresia
14.1.5.3 Congenital Hiatal Hernia
14.1.6 Pathologic Findings
14.1.6.1 Gastro-Oesophageal Reflux (GOER)
14.1.6.2 Hypertrophic Pyloric Stenosis (HPSt)
14.1.6.3 Other Stomach Conditions
14.1.7 Role of US
14.2 Bowel
14.2.1 Preparation and Requisites
14.2.2 Course of Investigation
14.2.3 Normal US Findings
14.2.4 Pathology
14.2.4.1 Congenital Anomalies
14.2.5 Acquired Obstructive Pathology
14.2.5.1 Meconium Ileus
14.2.5.2 Midgut Volvulus
14.2.5.3 Sigma Volvulus
14.2.5.4 Hernia
14.2.5.5 Intussusception
14.2.5.6 Masses and Tumours
14.2.6 Inflammatory Conditions
14.2.6.1 Necrotising Enterocolitis (NEC)
14.2.6.2 Gastroenteritis
14.2.6.3 Henoch–Schönlein Purpura
14.2.6.4 Appendicitis
14.2.6.5 Crohn’s Disease
14.2.6.6 Colitis
14.2.6.7 Other Inflammatory Bowel Conditions
14.2.6.8 Bowel Trauma
14.2.7 Mesentery
14.2.7.1 Mesenteric (Peritoneal) Masses
14.2.7.2 Abscesses
14.2.7.3 Twisted Appendices Epiploica
14.2.8 Mesenteric Lymph Nodes
14.2.9 Free Intraperitoneal Air
14.2.10 Free Intraperitoneal Fluid: Ascites
14.2.11 Mesenteric Vessels
15: Ultrasound of the Urogenital Tract in Neonates, Infants, and Children
15.1 Requisites
15.1.1 Indications
15.1.2 Preparation
15.1.3 Transducers
15.1.4 Positioning
15.1.5 How to Investigate
15.1.5.1 Diuretic US
15.1.6 Contrast-Enhanced Voiding Urosonography (ce-VUS)
15.2 Normal Findings
15.2.1 Bladder
15.2.2 Kidney
15.2.2.1 Normal Variants
Duplex Kidney
Ectopic Kidneys
Renal Agenesis
Fusion Anomalies and Other Rare Findings
15.3 Pathology of the Kidney
15.3.1 Congenital Conditions
15.3.1.1 Dysplasia/Hypoplasia
15.3.1.2 Cystic Renal Disease
Inherited/Congenital Cystic Disease
Acquired Cystic Kidney Disease
15.3.1.3 Alteration of Urinary Drainage
Urinary Tract Dilatation (UTD) or Pelvicalyceal Dilatation/Distention (PCD)
Pelvi-ureteric Junction Obstruction (PUJO)
Uretero-Vesical Junction Obstruction (UVJO)/Obstructive Megaureter (POM/MU)
Posterior Urethral Valve (PUV)
Vesico-Ureteric Reflux (VUR)
Secondary Obstruction
15.3.2 Inflammatory Renal Parenchymal Conditions
15.3.2.1 Pyelitis
15.3.2.2 Acute Pyelonephritis (aPN)/Interstitial Nephritis
15.3.2.3 Necrosis and Abscess Formation
15.3.2.4 Scarring
15.3.2.5 Tuberculosis
15.3.2.6 Xanthogranulomatous Pyelonephritis
15.3.2.7 Glomerulonephritis/Nephrotic Syndrome
15.3.3 Vascular Conditions
15.3.3.1 Renal Artery Stenosis
15.3.3.2 Arteriovenous Fistula (AVF)
15.3.3.3 Infarction
15.3.3.4 Renal Vein Thrombosis
15.3.4 Nephrocalcinosis
15.3.5 Urolithiasis
15.3.6 Other Important Renal Parenchymal Disease
15.3.6.1 Haemolytic Uremic Syndrome (HUS)
15.3.6.2 Glomerulonephritis/Nephrotic Syndrome
15.3.6.3 Scars, Cirrhotic Kidney
15.3.7 Renal Failure (RF)
15.3.8 Renal/Urinary Tract Trauma
15.3.9 Renal Tumours
15.3.9.1 Benign Tumours
15.3.9.2 Pre- or Semi-Malignant Tumours
15.3.9.3 Malignant Tumours
15.4 Renal Biopsy and Interventions
15.4.1 Renal Biopsy
15.4.2 Drainage/Nephrostomy
15.4.3 Postoperative Imaging
15.4.3.1 After VUR Treatment
Cystoscopic Treatment
Antireflux Surgery
15.4.3.2 Findings after Pyeloplasty
15.4.3.3 After Various Interventions
15.5 Renal Transplant
15.5.1 Normal US Findings in Renal Transplant
15.5.2 Pathologic US Findings
15.6 Adrenal Glands and Pararenal Space
15.6.1 General Remarks
15.6.2 Typical Normal US Finding
15.6.3 Pathologic Findings
15.6.3.1 Adrenal Gland Haemorrhage
15.6.3.2 Inflammatory Condition
15.6.3.3 Tumours
Adrenal Cysts
Adrenal Adenoma
Neuroblastoma
Ganglioneuroma
Phaeochromocytoma
Adrenal Carcinoma
Role of US
15.7 US of Urinary Bladder
15.7.1 Requisites
15.7.2 Pathologic Findings
15.7.2.1 Atypical Shape (Neurogenic Bladder, “Valve Bladder”)
15.7.2.2 Polyps
15.7.2.3 Bladder Tumours
15.7.2.4 Calcification in/of Bladder
15.7.2.5 Ureterocele
15.7.2.6 Persisting Urachus
15.7.2.7 Megaureter
15.7.2.8 Infravesical Obstruction and Urethra
15.7.2.9 Inflammation
15.7.2.10 Traumatic Changes
15.7.2.11 Vesico-Ureteric Reflux
15.7.3 Paravesical Changes
15.7.3.1 Abscess Formations
15.7.3.2 Tumours of Paravesical Region
15.7.3.3 Cystic Perivesical Structures
15.7.4 Role of US
15.8 US of Male Genitals
15.8.1 US Technique
15.8.2 Normal Findings
15.8.3 Common Pathologic Findings
15.8.3.1 Hydrocele
15.8.3.2 Undescended Testes
15.8.3.3 Varicocele
15.8.3.4 Cystic Dysplasia of Rete Testis and Seminal Vesicles
15.8.3.5 Testicular and Paratesticular/Epididymal Cysts/Spermatocele
15.8.3.6 Microlithiasis
15.8.4 Inflammation—Orchitis, Ependymitis
15.8.5 Scrotal Trauma
15.8.6 Torsion
15.8.6.1 Torsion of Appendages
15.8.6.2 Inguinal Hernia
15.8.7 Testicular Tumours
15.8.8 Role of US and Additional Imaging
15.9 Female Genitals
15.9.1 Indications
15.9.2 Requisites
15.9.3 Transducers
15.9.4 How to Perform Investigation
15.9.5 Normal Findings
15.9.5.1 Sonogenitography
15.9.6 Pathologic Findings
15.9.6.1 Congenital Malformations
Vaginal Septum and Duplications
Vaginal Atresia
Vaginal Fistula
Other Vaginal Malformations
Vaginal Aplasia
Uterine Malformations
Ovarian Malformations
15.9.6.2 Inflammatory Conditions of Female Genitalia
15.9.6.3 Genital Tumours and Space Occupying Lesions
Cysts
Teratoma
Other Genital Tumours
Rhabdomyosarcoma
15.9.6.4 Traumatic Changes
15.9.6.5 Other Specific Important Entities of Female Genitalia in Childhood
Ovarian Torsion
Pregnancy
15.9.6.6 Role of US/Additional Investigations
16: Neonatal and Paediatric Hip US
16.1 General Remarks
16.2 Examination Technique
16.2.1 Hip US According to Graf
16.2.2 Modified Graf Classification (Rosendahl)
16.2.3 Hip US According to Harcke
16.2.4 Femoral Head Coverage According to Morin (and Modified Morin-Terjesen)
16.2.5 3DUS for DDH Assessment
16.2.6 Assessment of Joint Effusion, Capsular Thickening, Perthes, Arthritis and Others
16.3 Normal Anatomy
16.3.1 US Criteria in Graf
16.3.2 Rosendahl Modification
16.3.3 Normal Findings During Harcke Investigation
16.3.4 Anatomic Landmarks and Normal Limits for Measuring Femoral Coverage
16.4 Hip US in Older Children
16.5 Pathologic Findings
16.5.1 Developmental Dysplasia of the Hip (DDH)
16.6 Other Conditions of Hip Joint
16.6.1 Arthritis and Inflammation of Hip Joint
16.6.1.1 Capsular Thickening
16.6.1.2 Joint Fluid/Effusion
16.6.2 Hip Osteoarthritis
16.6.3 (Femoral Head) Epiphysiolysis/Slipped (Capital Femoral) Epiphysis
16.6.4 Perthes Disease
17: Musculoskeletal and Other Small Part US in Childhood
17.1 Investigation of Bones, Joints, Tendons
17.1.1 Requisites and Technique
17.1.2 Typical Normal Findings
17.1.3 Pathologic Findings
17.1.3.1 Fracture
17.1.3.2 Joint Effusion
17.1.3.3 Arthritis
17.1.3.4 Trauma
17.1.3.5 Cysts
17.1.3.6 Inflammation
17.1.3.7 Neoplasia
17.2 Other Small Part Applications
17.2.1 General Remarks
17.2.2 Foreign Bodies
17.2.3 US of “Lumps and Bumps”
17.2.4 US for Peripheral Vessels
17.2.5 US of the Paediatric Breast
17.2.6 US of Muscles
17.2.6.1 Traumatic Changes: Haematoma/Tear/Rupture
17.2.6.2 Inflammatory Myositis
17.2.6.3 Other Structural Changes: Fibro-Dystrophic or Atrophic Muscles
17.2.7 Miscellaneous Other Applications
18: US of Peripheral Nerves in Childhood
18.1 General Remarks
18.2 US Technique
18.3 Nerve Anatomy/Structure
18.3.1 Normal US Findings
18.3.2 Most Important Clinical Questions in Children
18.4 Cranial Nerve US
18.4.1 Optic Nerve (Cranial Nerve II)
18.4.2 Facial Nerve (Cranial Nerve VII)
18.4.3 Vagal Nerve (Cranial Nerve X)
18.5 Cervical and Brachial Plexus
18.6 US of Peripheral Nerves of Extremities
18.6.1 Median Nerve
18.6.2 Ulnar Nerve
18.6.3 Radial Nerve
18.6.4 Femoral Nerve
18.6.5 Sciatic Nerve
18.7 Nerve Trauma
18.8 Peripheral Nerve Tumors
18.8.1 Neur(in-)oma
18.8.2 Benign Peripheral Nerve Tumors
18.8.3 Schwannoma
18.8.4 Neurofibroma
18.8.5 Nerve Sheath Ganglion
18.8.6 Malignant Peripheral Nerve Tumors
Part IV: Miscellaneous
19: US-Guided Interventions and Invasive US Procedures and Respective Follow-Up
19.1 General Aspects
19.1.1 Requisites
19.1.2 Other Important Needs
19.1.3 Precautions and Preparations
19.2 US-Guided Filling of Structures for Diagnostic or Therapeutic Purpose
19.2.1 General Remarks for Assessing Physiologic Cavities (For Example, Bladder, Vagina, Intestines, Stomach, etc.)
19.2.2 Diagnostic Sonographic Enema
19.2.3 Therapeutic Sonographic Enema
19.2.4 US Genitography
19.2.5 Contrast-Enhanced Voiding Urosonography (ce-VUS)
19.2.6 Other Intracavitary Contrast Applications
19.2.7 Intravenous ce-US
19.3 Biopsies and Punctures
19.4 Drainage
19.5 Vascular Access
19.6 Lumbar Puncture
19.7 Foreign Body Removal
19.8 US Guidance for Local Anaesthesia
20: Normal Values as Relevant for Paediatric US
20.1 Introduction
20.2 Normal Values in Paediatric Neurosonography
20.3 Normal Values in US of the Paediatric Neck, Including Also Lymph Nodes
20.4 Normal Values in Paediatric Echocardiology
20.5 5. Normal Values in the Paediatric Abdomen (Excluding Urogenital Tract)
20.6 Normal Values in the Paediatric Urogenital System
20.7 Normal Values for US of Paediatric Small Parts and Musculoskeletal System
20.8 Additional Reading

Citation preview

Pediatric Ultrasound Requisites and Applications Michael Riccabona Editor Second Edition

123

Pediatric Ultrasound

Michael Riccabona Editor

Pediatric Ultrasound Requisites and Applications Second Edition

Editor Michael Riccabona Department of Radiology, Division of Pediatric Radiology Medical University Graz and University Hospital Graz Graz Austria

ISBN 978-3-030-47909-1    ISBN 978-3-030-47910-7 (eBook) https://doi.org/10.1007/978-3-030-47910-7 © Springer Nature Switzerland AG 2014, 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface for the Second Edition

It is a couple of years that the first edition has been published. Since then, there have been new developments in ultrasound that also affected paediatric practice; furthermore, point-of-care ultrasound (POCUS) has enormously expanded with nearly all specialties performing focused US exams trying to improve their clinical practice. With this development, the overall expenditure for clinical US has grown remarkably—in some countries, US is becoming the most expensive imaging modality in terms of total costs to the health care system, simply because so many exams are done. In paediatrics, nearly every office has at least a small US device which is used not just for the “traditional” standard indications such as screening but also increasingly to improve initial diagnosis trying to streamline further work-up and patient management. In the light of these developments, the new edition has been restructured and a dedicated chapter on POCUS has been added. All the chapters have been revised and new aspects have been included, particularly remarks on respective and/or new applications of POCUS, US-elastography, and contrast-enhanced US have been addressed. Furthermore, as POCUS often addresses small parts or nerves and not just abdominal queries, these chapters have been redone and a dedicated chapter on US of peripheral nerves has been added. Finally, the new lung US applications have been introduced and illustrated as well. So I and my (co-)authors hope that this new edition will serve as helpful as the first edition, still maintaining the same format as a relatively small but comprehensive booklet also accessible in electronic format. Reflecting the size of the book, more detailed information on some special issues will have nevertheless to be retrieved from established textbooks on paediatric US and paediatric radiology. Again, I want to thank Springer for enabling this new edition, my colleagues at work for their input and suggestions, the work and input and images from my co-­ authors, and my wife Barbara for her patience and support. I hope that the readers will find this booklet helpful for their daily needs and it will contribute to improve dedicated paediatric US for all children in need. Graz, Austria March 2020

Michael Riccabona

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Acknowledgements

I want to thank my (co-authors) Prof. Brian Coley (Cincinnati, USA) and Dr. Gerolf Schweintzger (Leoben, Austria) for providing additional and new images for the various chapters and especially Prof. Brian Coley for checking my English and editing the booklet for proper use of English language.

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Contents

Part I Basics/Theory/Methods 1 US Physics��������������������������������������������������������������������������������������������������   3 Michael Riccabona 2 US Methods, Artefacts, Biologic Effects, Practice����������������������������������  17 Michael Riccabona 3 (Color) Doppler US: Theory, Artefacts, Typical Applications in Childhood ����������������������������������������������������������������������������������������������  39 Michael Riccabona 4 Contrast-Enhanced US, and Ultrasound Elastography in Childhood ����������������������������������������������������������������������������������������������  59 M. Riccabona and H. J. Mentzel 5 Paediatric Limited Field of View US/Point of Care US (POCUS) and Emergency US: When, How and for What ��������������������  77 Michael Riccabona, Gerolf Schweintzger, and Brian Coley Part II Diagnostic Flow Charts, Imaging Algorithms, and Graphs 6 Imaging and Imaging Algorithms for Common Queries in Childhood ����������������������������������������������������������������������������������������������  89 Michael Riccabona 7 Measurements and Volume Calculations: Basic Considerations, Graphs and Illustrations for Standardisation ������������ 103 Michael Riccabona Part III US Investigations of the Various Organs 8 Neurosonography in Neonates, Infants and Children���������������������������� 113 Michael Riccabona 9 US of the Neonatal Spinal Canal and Cord �������������������������������������������� 167 Michael Riccabona 10 Ultrasound of the Neck in Childhood������������������������������������������������������ 179 Michael Riccabona ix

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11 Basics of Paediatric Echocardiography �������������������������������������������������� 205 Martin Köstenberger, Andreas Gamillscheg, and Michael Riccabona 12 Ultrasound of the Chest���������������������������������������������������������������������������� 231 Michael Riccabona 13 Upper Abdominal US in Neonates, Infants and Children: (Excluding the Kidneys)���������������������������������������������������������������������������� 263 Michael Riccabona 14 US of the Gastrointestinal (GI) Tract������������������������������������������������������ 335 Michael Riccabona 15 Ultrasound of the Urogenital Tract in Neonates, Infants, and Children���������������������������������������������������������������������������������������������� 375 Michael Riccabona 16 Neonatal and Paediatric Hip US�������������������������������������������������������������� 471 Gerolf Schweintzger, Brian Coley, and Michael Riccabona 17 Musculoskeletal and Other Small Part US in Childhood���������������������� 487 Michael Riccabona, Gerolf Schweintzger, and Brian Coley 18 US of Peripheral Nerves in Childhood���������������������������������������������������� 513 Jörg Jüngert and Michael Riccabona Part IV Miscellaneous 19 US-Guided Interventions and Invasive US Procedures and Respective Follow-Up ������������������������������������������������������������������������ 525 Brian Coley, Gerolf Schweintzger, and Michael Riccabona 20 Normal Values as Relevant for Paediatric US ���������������������������������������� 543 Michael Riccabona, Brian Coley, Martin Köstenberger, Hans-­Joachim Mentzel, and Gerolf Schweintzger

Part I Basics/Theory/Methods

1

US Physics Michael Riccabona

1.1

US Waves

Definition  • Mechanical waves, usually created by electric current applied to piezoelectric crystal in transducer, used to emit sound waves and receive reflected echoes. • Frequencies used in diagnostic medicine range from 1 to 20 MHz. Sound Velocity  • Depends on material; the higher the density, the higher the sound velocity. • In air, sound velocity is approximately 330 m/s; average sound velocity of human (soft) tissue = 1540 m/s. • Some new devices allow for choosing the respective sound speed, used, e.g., for tissue analysis/fat quantification.

1.2

Propagation and Modulation of US

US energy emitted into tissue is handled differently between different tissue layers: modulated, partially absorbed, partially transmitted and reflected on border of different tissue. The most important principles for propagation phenomena:

M. Riccabona (*) Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_1

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M. Riccabona

1.2.1 Acoustic Impedance Relation of sound pressure to resulting molecular motion. Tissues with high density need less energy to start undulating than tissues with little density.

1.2.2 Impedance Change Arises when US waves cross borders between tissues of different acoustic impedance.

1.2.3 Reflection Observed when US wave meets border layer between tissues of different impedance; reflection occurs according to mirroring rules (Snell’s law). Degree of reflection depends on surface structure (e.g. smooth or rough and straight or bent), angle between tissue surface and US beam.

1.2.4 Absorption US waves gradually weakened when crossing different media. Loss depends on tissue density and content, and is proportional to US frequency (greater loss = less penetration): • Low frequency: good penetration but decreased resolution. • High frequency: decreased penetration but increased resolution.

1.2.5 Deflection When US wave passes small opening, US beam scattered depending on dimension of this “lens”; scattered sound waves may cause artefacts.

1.2.6 Focus In modern diagnostic US, multiple crystals create multiple individual US waves. These need to be focused at specific areas in order to create detailed images of defined area. Focusing achieved by: • Hollow mirror effect: US field gets smaller and smaller by concave shape of emitting crystals. • Additional lenses. • Electronic focusing by dedicated steering of single elements with proper timing.

1  US Physics

5

Table 1.1  Resolution versus frequency—orienting numbers Frequency (MHz) 3.5 5 7.5

Resolution (mm) Axial 7 0.6 0.4

Lateral 2 1.2 0.8

Depth (mm) 160 100 50

The higher the frequency, the better the resolution; lateral resolution always less than axial Penetration depth also depends on frequency: lower frequencies have a deeper penetration

Optimising Focal Zone  Single and multiple focus techniques available—need to be constantly optimised/updated during investigation for optimal results. Remark The newest technology: e.g. “retrospective transmit beamforming”, “all in focus”, or “confocal” emit and receive, based on new transducer and beamformer technology and increased processing speed and capabilities—no individual focus setting necessary, although still beneficial in some detailed investigations (e.g. “inFocus” by Siemens, “cSound” by GE).

1.2.7 Resolution Definition  Minimal distance between two neighbouring structures that can still be discriminated. Two different phenomena • Lateral resolution: discrimination of objects side by side at same depth: –– Mostly dependent upon beam width. • Longitudinal and axial resolution: discrimination of objects in direction of US beam. –– Mostly dependent upon frequency: the lower the frequency, the worse the resolution (see Table 1.1).

1.3

Emission, Transmission, Reception and Amplification

1.3.1 Emission US waves emitted by transducer crystals contain 64–512 crystals in conventional US: • Specific modern transducer technologies: matrix transducers, 1.5D arrays, 2D arrays; may contain up to several thousand single crystals. • Split crystal transducers  =  modern technology to create multiple “elements”, usually for 3D/4D- or some 2D arrays.

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• Future specific transducers (developed for 3D-/4DUS) >10,000 single elements. • Recently, a new technology is gaining interest—capacitive micromachined ultrasonic transducers (CMUT): relatively new concept based on metalized silicon, allowing smaller transducer size at broader bandwidth (e.g. for intravascular probes). Good contact of transducer to skin mandatory for optimal US transmission into tissue; achieved by surface shape of transducer, material of transducer membrane and (sufficient) US gel to eliminate air.

1.3.2 Transmission US waves partially absorbed and partially reflected, the latter particularly at border of different tissues. Tip  Transmission improved by high water content in tissue (= good hydration).

1.3.3 Reception After emission of US wave—crystal function changed to receive. Reflected US waves create electric signal within crystal; amount of electric energy depends on amount of reflected sound energy: • More reflected sound—more electric impulse—brighter, more echogenic signal. • Moderate reflection—poor echo. • No reflection—echo free or anechoic. Spatial location of reflecting structure defined by time interval between emitting and receiving: • The deeper a structure, the longer the sound beam needs to travel to it and back. • Measured time between sound emission and reception of a certain reflected energy defines position/depth of respective structure within US field/image (in B-Mode US). The longer sound takes to travel, the deeper position of respective structure.

1.3.4 Amplification Electric signals created by incoming reflected US waves in crystals amplified within US system for further processing.

1  US Physics

1.4

7

Signal Processing

Raw signal processed using multiple parameters/methods.

1.4.1 Preprocessing Performed during investigation, includes electronic modulation of signal quality during sending (beam forming) as well as modulation of sensitivity of crystal during receiving.

1.4.2 Post-Processing Performed once data collected, i.e. on frozen image. Many different electronic modulation tools can be applied to improve image quality, modulate contrast, weigh grey levels, change scales, etc.

1.4.3 Time Gain Compensation (TGC) Reflected echoes from deeper areas have to pass through much more tissue, therefore suffer from more absorption: these signals are proportionally amplified to compensate for signal loss. Note  TGC should be constantly optimised during investigation, varies with echodensity/absorption of more superficial transmitted structures (Fig.  1.1). Modern “automated image optimisation” tools/“magic buttons” may help-however, cannot (yet) replace operator.

Fig. 1.1  TGC—image example (a) incorrect (b) correct TCG adaptation. (a) Incorrect image of the magnified retrovesical cross-section view without proper TGC adaptation—causes echogenic retrovesical structures reducing differentiation of anatomy; particularly the dilated left ureter cannot be clearly depicted (TCG settings recognisable by the dotted line on the right side of the image). (b) Same section as in (a)—TGC adapted: better image quality—the slightly prominent left ureter clearly visible distal as circular hypoechoic structure

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1.4.4 Sound Energy = Output Maximum output intensity defined by equipment depending on manufacturer. To avoid unnecessary overexposure of tissue/deterioration of image: decrease US intensity as much as possible. Definable partially by presets (e.g. foetal exams, transcranial/transfontanellar brain US, US of eye/testis) or individually at beginning of examination. MUST be shown on display—usually as percentage of maximum output gain or in Watts. Note  Every investigation should be performed at lowest possible sound output. Impact of sound energy on tissue important to maintain safe sound pressure levels: • Parameters depend on many factors such as focal zone, frequency and output gain setting. • New indices established: reflect impact of US energy on tissue (mechanical index = MI, thermal index = TI); should (must) be displayed during every investigation—monitor/observe closely. • In general, MI/TI should be kept below 1 to maintain safe sound exposure levels (rule of thumb); short higher exposures are sometimes unavoidable (e.g. harmonic imaging, Doppler …, keep as short as possible!) –– For further details, see biological effects.

1.4.5 Gain Defines overall amplification of incoming signals: • Optimise receive gain individually depending on output gain, patient, anatomy and area of investigation.

1.4.6 Frame Rate/Persistence Persistence  Defines speed of image update (e.g. how many raw images are used to calculate the image on screen): • High persistence (information from series of individual images used to create final displayed image)—increased tissue density information and resolution—at cost of slower update of individual displayed image. Frame Rate (Hertz, Hz)  Depends heavily on transducer technology and image calculation software; usually US investigations operate at 4–60 Hz; faster frame rates are possible, e.g. for cardiac studies.

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• High frame rate—fast series of individual images, reduced susceptibility to motion artefacts—but usually at cost of slightly reduced resolution and a “noisier” image. Note  New image acquisition and reconstruction technologies (e.g. sectorial image acquisition/insonation …) will further speed up frame rates.

1.5

Components of US Device

Consists of emit and receive partition as well as transducers connected to system via cables. Also: display monitor, keyboard, memory/data storage and documentation ability.

1.5.1 Transducers Different types depending on underlying technology: mechanical, electronic and combined transducers. Modern transducers usually use a range of frequencies, with an individually adaptable diagnostic effective middle frequency—called multifrequency transducers. Sector Transducers Small active surface (footprint) where sound beams emitted in sector format (Fig. 1.2): • Causes poor image quality in near field, improved visualisation of deeper fields. • Particularly useful for structures with only small access area (e.g. echocardiography—access between ribs, or brain US—transfontanellar access). Different techniques used to create sector-like field: • Mechanical devices that make crystal (or series of crystals) rotate or wobble: –– Sector angle usually between 60° and 120° used for imaging. Note: Mechanical transducers may deteriorate over time by physical use—not only proper handling but also exact production and alignment important (Fig.  1.2a). Important to freeze image (i.e. transducer) whenever one does not actually investigate to prevent early transducer deterioration/aging. However, these are rarely still in use. • Electronic-phased array transducers consist of series of crystals: –– By individual steering of consecutive crystals with varying time intervals (presently most common technique), effective US beam can be directed in many directions creating sector-like imaging field (Fig. 1.2b).

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Fig. 1.2  Sector transducers—all creating a sector-like triangular image; good for small footprint access with wide view in far field. (a) old fashioned conventional sector: sector-like images created by dedicated array design or wobbling of a normal plane array. The wobbler technique hardly used anymore. Image is in a sector format; the shaded area represents the part of the structure that will be displayed on the monitor. (b) Phased/electronic (vector/sector) transducer: most commonly used format (alternatively mostly micro-curved arrays used). Image created by electronic steering of parallel-placed single elements. (c) Annular array: annular concentric US array which is shaped by specific lenses creating a very homogenous focal zone throughout the image field

• Annular array transducers—combination of mechanical and electronic technology: –– Various concentric rings of crystals selectively activated during scanning process create sector-like field with homogeneous focus zone throughout entire imaging field (Fig. 1.2c). • “Vector format”—different steering of an electronic sector transducer –– Opening up the near field to a vector like format thus enabling/improving near-field image Linear Array Transducers • Parallel linear US beams created by multiple crystals create rectangular image frame (Fig. 1.3a): –– Homogeneous resolution throughout entire imaging field, particularly valuable for near-field assessment. –– Generally used for superficial structures (e.g. small-part applications, cervical vessels, infant hips, lymph nodes, soft tissue processes and bowel/appendiceal US). • New techniques allow for “phasing” of electronic linear transducer—create a “virtual sectorial” image (“trapezoid”) = larger field of view in far field, at cost of frame rate and penetration, and also less homogeneous lower resolution image in far field (Fig 1.3c).

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a

b

Monitor image

Linear transducer Field of sound

c

Targeted object

Fig. 1.3  Transducers. (a) Linear transducer: parallel sound waves create a rectangular image. (b) Curved(linear) array transducer: transducer elements assembled in slightly curved fashion; transducer surface thus is bent; the radius may vary creating a more or less trapezoid image that is wider in far field than in near field. Combines benefits of linear and sector transducers (c) Trapezoid/ virtual sectorial/wide view/phased image of linear transducer

Curved Linear Array • Crystals aligned on curved surface—diverging US waves create sector-like imaging field (angle depends on radius of curvature); the larger surface (than sector transducer) offers good near-field information: –– Combines abilities and benefits from sector and linear transducers. –– Offers reasonable near-field resolution at large field of view at depth (Fig. 1.3b). –– Typical application: abdominal US (and brain with a “micro-curved”—then observe the risk of compressing brain and sinus).

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Note  May cause problems by compression, and more difficult to handle/entirely attach (some pressure needed—may be less well tolerated by young kids and my compress surface/superficial structures). Other Transducers • Matrix—1.5-/2-dimensional arrays: enable sound emission in two perpendicular planes by assembling elements in parallel rows: –– Allow volume scanning (see 3DUS). –– Improve lateral (out of plane/elevational plane) resolution by bidirectional focusing of US beam. –– Parallel columns of elements allow for simultaneous handling of different tasks (improving frame rate, e.g. for image compounding or colour/duplex/ triplex Doppler) by splitting individual operation modes to different parallel rows or crystals. • Intracavitary probes: mainly intravascular or endoscopic probes, transrectal/ intravaginal probes. –– Usually very small design, thus less elements. –– Often higher frequencies—better resolution than with transabdominal/thoracic access but at restricted penetration. –– Enable visualisation of areas impossible to properly depict by standard access. –– Attached to endoscopic devices/intravascular catheters. –– Often limited use for paediatric applications, as other access often works sufficiently and size relatively large for paediatric cavities. –– Dedicated small paediatric devices rarely available (e.g. for transoesophageal echocardiography, transrectal pelvic floor US). –– Some applications uncommon, non-existent or not accepted in paediatrics (e.g. transvaginal US).

1.5.2 Other Parts of US Device • • • • • •

Keypad (may be mobile and flexible). Monitor (may be mobile and flexible, can and must be adjustable). Printer/CD recorder. In-/output options. Cooling device with filters (need to be cleaned regularly). Potentially gel bottle warming device and transducer stands.

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Modern US Techniques

Today available on practically all new devices • Need to know and understand them to avoid wrong applications, choose proper settings and approach, and recognise potential associated artefacts.

1.6.1 High-Resolution US (HR-US) • Uses relatively high frequencies, usually multifrequency broadband transducers, with depth and focus depending on variations of central frequency. • Additional mechanical or electronic lenses improve lateral resolution by improved beam focusing, thus increasing penetration and resolution. • HR-US particularly valuable in paediatric US and small-part imaging.

1.6.2 Image Compounding • Also known as sono-CT or cross-beam imaging—uses US beams from various directions or varying frequencies to assess same area (Fig 1.4a). All information averaged and calculated into one single image, similar to CT algorithms. • Particularly helpful for reducing artefacts and improving depiction of subtle grey scale changes/differences. • However, intrinsically reduces frame rate. May also alter image impression and impact on appearance/artefacts (e.g. reduces shadowing behind calcifications, effects anisotropy phenomenon …) (Fig 1.4b, c). Harmonic Imaging

a

b

Image compounding

c

Fig. 1.4 (a) Schematic drawing explaining how “compounding” works, (b) Shadow behind echogenic foci at renal hilus, conspicuously depicted by Harmonic imaging (b), which disappears when using high scale Image Compounding (c)

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1.6.3 Harmonic Imaging (HI) • Has become widespread and common, using first harmonic response of resonating reflectors instead of original reflected echo for creating US image. • Reduces penetration and needs slightly higher output gain, but HI significantly reduces noise—as signal for imaging is created by resonating individual structure itself. • Improves border delineation and differentiation of liquid structures, enhances grey scale differences. • Commonly used in combination with HR-US/compounding; furthermore essential for contrast-enhanced US (ce-US). Note  Though initially applied mainly to adults in poor scanning conditions (caused by overlying structures or adjacent gas), HI is now routinely applied in paediatric US, too (Fig. 1.5).

Fig. 1.5  Harmonic imaging (HI). (a) Normal grey scale cross-section image of a kidney (+2) with a slightly dilated renal pelvis (+1): somewhat hazy image with poor quality. (b) Same infant and same section as in (a) acquired with HI: more conspicuous image with better delineation of the dilated pelvis and the renal borders; also the cortico-medullary differentiation is accentuated (beware of imaging technique induced artificial “pseudonephrocalcinosis”)

1.6.4 Extended Field of View US • Also known as panoramic imaging or freestyle US.  Adds serial consecutive neighbouring US images into one big overview. • Based on calculation of transducer motion from picture inherent information— thus two consecutive images can be aligned in proper anatomic order; continuous display of even very large structures is achievable (Fig. 1.6). Not only useful for comprehensive overview of gross pathology or anatomy but also for displaying long/large structures or measuring structures too large for field

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Fig. 1.6  Extended field of view US. (a) Measurement of liver length in anterior axillary line: due to large size, this can only be reliably achieved by using “extended field of view”; additionally a more conspicuous view of the entire organ with the kidney can be achieved. (b) Enlarged urinary bladder sagittal view: conspicuous view and reliable measurement of this megacystis

of view of conventional transducers (e.g. large transplant kidney, severe splenomegaly and huge tumours).

1.6.5 US Texture Analysis Tries to improve US ability to differentiate and analyse tissue texture. Still under development, not routinely applied or available on all devices. • Quality of reflective echoes from dedicated/individually defined area is assessed using various algorithms to compare all sonographic attributes, or changes in sound velocity. • After comparison with normal standardised echotexture or potentially available information from previous scans as well as other healthy organ regions, differences in tissue texture are displayed. • Potentially improve detection and characterisation of specific tissue areas (“sono-histogram”). • Similar principle is applied to quantify flow based on CDS information—only offered by some vendors. • A new application of this approach is the upcoming sonographic liver fat quantification: still under research, but as today no established applications—particularly in paediatrics.

1.6.6 P  otential Future for Other Modern Paediatric US Applications A number of potential applications on horizon: US-guided drug delivery, optic-­ acoustic imaging, etc.

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Most presently under preclinical research conditions, some starting in human trials, some introduced to adult scanning: • Image fusion techniques for diagnostic and interventional procedures—already introduced to adult scanning and intervention, rarely used in kids as more cumbersome (motion artefacts …). • Liver fat quantification—recently introduced by some vendors, just being studied in adults. Two main methods reported: controlled attenuation parameter (CAP—based on transient elastography—see Chap. 4) or Acoustic Structure Quantification (ASQ—based on analysis of echo amplitude distribution, also useful for other structural tissue analysis). May hold potential in obese children/ adolescents, or children with other metabolic conditions, too. Other approaches usually based on speed of sound estimation, backscatter coefficient and attenuation parameters. • US-guided drug delivery: UCA is used as carrier for attached drugs. Arrival of drug-loaded UCA at desired location is detectable by ce-US, then high-energy sound pulse is activated to destroy UCA/carrier molecule, thus deliver drug locally to targeted area—reducing systemic drug interactions/adverse advents. –– Foreseen for oncology but also potential for any other focal disease (e.g. inflammatory). • Opto-acoustic imaging, US thrombolysis, etc., many future applications on horizon but beyond scope of booklet.

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US Methods, Artefacts, Biologic Effects, Practice Michael Riccabona

2.1

A (Amplitude)-Mode

Oldest US technique, still used today in ophthalmology (for measuring various small structures of eye). Technique  Emitted US impulse reflected at major interfaces, signal received during transmission break. Graph illustrates travel duration of US beam on x-axis and intensity of reflected echoes as amplitude spikes on y-axis (Fig. 2.1).

2.2

(T)M-Mode (Time-Motion-Mode)

Used to show positional changes of reflecting interfaces over time. Principle  On x-axis of monitor graph, changes in position of individual image pixels displayed; change in intensity of reflected echo is encoded by variation in brightness, whereas time is encoded on y-axis. Method frequently used in echocardiography and in some dedicated applications, e.g. for assessment of peristalsis or motion (e.g. ureteral peristalsis, diaphragmatic motion) (Fig. 2.1c).

M. Riccabona (*) Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_2

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Fig. 2.1  US modes. (a) A (amplitude)-Mode—oldest US technique: US signals emitted along single line, amplitude of reflected echo encodes spike height on y-axis, whereas depth of origin of reflection from individual structures encoded on x-axis (time between emission and receive). (b) B (brightness)-Mode: transducer emits sound waves; the reflected echoes are received. Energy of echo encodes brightness of respective pixel on monitor; position of respective pixel calculated from individual travel time (i.e. time between sound emission and receiving, with known sound speed in tissue). (c) M (motion)-Mode: US image (of a prominent ureter, cross section through bladder) shows a dotted line defining the section where changes (i.e. motion, in this case ureteral peristalsis) over time are displayed as graph in lower part of image (blue). Originally this was applied in echocardiography without orienting B-Mode image, just displaying the lower graph to analyse heart wall or valve movements

2.3

B (Brightness)-Mode

The commonly used real-time US imaging technique (Fig. 2.1b). Technique  Transmitted US waves reflected when encountering various interfaces: • Brightness of individual image pixels defined by intensity of reflected echoes (the stronger the echo, the brighter the corresponding pixel). • Position of pixels defined by direction of transmitted beam inducing individual echo (encoded on x-axis) and time between sending and receiving (depth, encoded on y-axis). • All reflected echoes displayed on monitor correspond to travel time within predefined beam direction—calculated sectional image. • Repetitive frequent updates of such sectional images create movie-like impression enabling what is called “real-time US”.

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Fig. 2.2  Doppler US. (a) Doppler scheme: US signal emitted; frequency shift of received echo measured, thus flow velocity and flow direction can be calculated using Doppler equation; for correct velocity estimation, angle between incoming US signal and movement direction of reflecting particle (i.e. mostly erythrocytes) must be measured. (b) Doppler display: besides audio signal typically Doppler information displayed as flow graph after spectral analysis using Fourier transformation. All velocities throughout spectrum are displayed at any time (of cardiac circle), with intensity encoding number of reflectors at the individual velocity. Y-axis encodes flow velocity; x-axis encodes time

2.4

Doppler Sonography

If sound reflected by moving interface, frequency of reflected wave shifted (Doppler effect). • Frequency shift depends on angle between sound beam direction and direction of motion, as well as velocity of moving particle/interface; shift defined by Doppler calculation (Fig. 2.2a). • Frequency shift of received echoes can be measured; thus flow direction and flow velocity can be calculated and displayed in various ways (Fig. 2.2b—also see Chap. 3)

2.5

Artefacts

2.5.1 General Remarks Artefacts caused by phenomena that interfere with image formation and cannot be sufficiently corrected: • Impair image (e.g. bowing artefacts, reflection artefacts). • Can also be diagnostically valuable (e.g. posterior enhancement/through transmission for identification of liquids, posterior shadowing for identification of calcifications). • Knowledge of artefacts essential for proper image interpretation.

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2.5.2 Common Artefacts 2.5.2.1 Side Loop Artefact Transducer does not only emit central beam but also side loops—can produce significant echoes when reflected by strong interfaces. Some of these echoes reflected into direction of central beam and received by transducer—these echoes appear projected into main beam, get used for image calculation, although deriving from structures out of main beam direction. Only cause image impairment when encountering highly reflective surface; respective echoes are displayed as if arisen from central beam (wrong position), usually only recognisable when occurring in fluid-filled or low-echogenicity structure. • Typical example: adjacent bowel gas surface alters image of gall bladder mimicking sludge. • Can be identified by change of transducer position (e.g. tilt transducer). • Can usually be eliminated by repositioning transducer and reducing gain, altering angulation, etc.

2.5.2.2 Bowing Artefact Arise by wrong projection of reflected echoes into anatomic incorrect position. Caused by oblique reflections of beam—reflected echo received by “wrong” crystal, position wrongly assigned for further processing. • Can usually be eliminated and identified by tilting of transducer.

2.5.2.3 Noise Definition Signal-like monitor appearance throughout image is created by electronic processing and amplification. Background noise is increasingly amplified with reduced signal strength (e.g. TGC adaptation or high-receive gain). Near limits of penetration: differentiation between noise and real signals may become impossible. Depending on gain settings, noise can also create artificial echoes within anechoic lesions such as fluid or cysts, making differentiation difficult or impossible—particularly when small. • For differentiation/identification: change focus position, output gain and transducer frequency. • Modern devices all offer some sort of noise filtering, which can be set to various intensities.

2.5.2.4 Marginal Shadowing Created by spherical structures with clear limit that exhibit significant acoustic impedance interval at its lateral borders—appears as line-like sound mitigation at lateral borders behind object.

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Physical cause—tangential impact of sound beam, additional scattering and reflection at lateral wall—then transmitted into deeper image sections. • Helpful for identification of cysts and tubular structures but may be mistaken for acoustic shadowing from small concretions, e.g. in gall bladder or kidneys (Fig. 2.3).

2.5.2.5 Posterior Enhancement—Increased through Transmission When sound passes through completely fluid-filled anechoic structure (or other structure with little sound attenuation), intensity of US beam is not altered by absorption and reflection: causes different echo intensity of area deep to such fluid-­ filled structures compared to adjacent area of same depth where US beam has been more attenuated by intervening tissue. TGC correction artificially adapts for intensity drop by depth—areas behind fluid displayed more echoic than surrounding structures. • Helpful to identify fluid/fluid-filled structures. Note  In order to properly assess tissue behind large fluid-filled structures, adaptation of TGC correction to account for this phenomenon is essential (Fig. 2.4). Fig. 2.3  Artefact—marginal shadowing, reverberations. Artificial anechoic lines originating from margins of venous sinus in this axial liver view not corresponding to any specific anatomic or pathologic findings. Note echoic spots with reverberations within liver indicating intrahepatic air/gas

Fig. 2.4  Artefact—through transmission. Artificially increased echogenicity behind fluid-filled bowel structure due to increase through transmission but deteriorating differentiation of respective structures (i.e. gastric duplication cyst)

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2.5.2.6 Reverberation Artefact Definition  Multiple reflections of sound travelling between two parallel layers with strong acoustic interfaces create repeated parallel echogenic lines that usually get weaker with depth: • Typically observed parallel to transducer at superficial layers (e.g. skin). • Can be reduced by altering focus and decreasing (output) gain. “Ring-down artefact” caused by resonance from gas; Short ring-down artefacts called comet tail artefact—special form of reverberation phenomenon, usually appears behind gas/air-filled structures. Reverberations most prominently seen with air interface—in lung ultrasound also known as “A-lines”. • Created by scattering and reflection of incoming sound beam with irregular reflections and noise behind sonographically non-penetrable surface (Fig. 2.5).

2.5.2.7 Increment or Slice Thickness/Beam Width Artefact Sound beam dimensions vary depending on kind of transducer, frequency and focus settings. Depending on relation of beam width with distance between solid and liquid structures, particularly at curved interfaces, small layer of low-degree echoes may appear. May mimic doubled/hazy wall structure, can be mistaken for sludge within fluid. A sort of partial volume phenomenon. • Can usually be eliminated by optimising focus setting and changing transducer or frequency.

Fig. 2.5  Artefact—reverberation/comet tail artefact and dorsal shadowing. Chest wall US: echogenic reverberations caused by aerated lung surface (↔) and dorsal shadowing (→) caused by ossified rib

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Fig. 2.6  Mirror image artefact. The echogenic border of skull bone causes mirroring of subcutaneous extracranial collection into subcalvarian intracranial compartment, mimicking a non-­existing intracranial collection. Note: artefacts from malattachment of transducer to bowed skin surface in upper right corner of image

2.5.2.8 Mirror Image Artefact Strong reflecting interface (mostly gas—i.e. air at lung base) met by sound beam in an angle around 45°—acts as acoustic mirror: artificial mirror images observed behind reflecting border due to prolonged travel duration of incoming signal (Fig. 2.6). • Also encountered on colour Doppler sonography (CDS), may be quite confusing. • Can be identified by changing transducer position/tilting transducer.

2.5.2.9 Shadowing If sound cannot penetrate and does not cause reverberations—area behind does not produce any echoes; i.e. it looks black like a shadow (see Fig. 2.6). • Useful for identifying stones, bones and other calcified structures—hinders assessment of area behind. Note  This artefact is significantly reduced when applying Image Compounding (see Fig. 1.4), and enhanced by Harmonic Imaging. May lead to misinterpretation!

2.5.2.10 Refraction Artefact Occurs when sound passes obliquely through an interface between tissues with significantly varying sound speed—thus refraction occurs (mostly solid/fluid interfaces or border between low- and high-echogenicity tissues). • Can cause duplication artefacts (duplicating structures)—also affects length measurements (e.g. kidney) (Fig. 2.7). • Refractive shadowing (see above—marginal shadowing artefact) caused by defocusing and variations in beam energy or intensity at edge of fluid-filled structures. • Can usually be eliminated by changing transducer position.

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Fig. 2.7  Refraction artefact causing two upper kidney poles (left longitudinal flank scan)—may be confusing, may cause wrong distance measurements

Fig. 2.8  Anisotropy effect: schematic drawing illustrating phenomenon

a

Anisotropy Property of directional structure Echogenicity depends on insonation angle

b

Fig. 2.9  Influence of anisotropy effect on image appearance: Different appearance of a tendon (arrow) when scanned orthogonally (a, echogenic—reflections from internal structure return to transducer) or obliquely with a tilted transducer position (b, hypoechoic—all echoes reflected out of receive field); phenomenon may also be reduced by cross beam imaging/image compounding

2.5.2.11 Anisotropy Occurs in tissues composed of very structured strong reflectors (e.g. fibrillar pattern)—echoes vary with insonation angle (Fig.  2.8), typically with muscles and tendons (Fig. 2.9). • Can usually be eliminated by changing transducer position/angulation. • Of utmost importance in musculo-skeletal US—if unrecognised may lead to incorrect interpretation (i.e. tear, etc.).

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Biologic Effects

2.6.1 General Remarks Biologic effects of diagnostic US based on physical phenomena caused by interaction of emitted US with tissue depending on frequency, wave length and output energy. Different devices may cause variable tissue impact with same application— because of different output gain settings/other device-specific presets.

2.6.2 Thermal Effects 2.6.2.1 Tissue Heating Caused by energy absorption—amount of temperature rise depends on output energy and intensity of sound field. Increases with higher frequency by deposition of higher amounts of energy in smaller volume (less penetration). Additionally, temperature-handling ability of tissue is important, e.g. vascularised and well-perfused tissue can better tolerate temperature changes than little or non-perfused tissue. Human tissue with highest thermal absorption is bone; therefore experiences highest temperature rise with secondary biologic effects particularly on neighbouring tissue. Note  Some heat generated by transducer itself is also transmitted to skin/tissue.

2.6.2.2 Biological Effects, Tissue Heating Even on routine diagnostic scans using modern diagnostic US devices, measurable increase in temperature may occur; particularly important for foetal examinations and (trans)cranial US. However, temperature that causes degeneration of proteins (i.e. >41.5 °C) or potentially cell death (>45 °C) does usually not occur in diagnostic applications. This effect must be considered when examining patients with high fever to avoid potential dangerous heat production; e.g. relatively short insonation of individual areas advisable. Commonly used parameter = thermal index (TI). Three different types of TI defined depending on tissue examined: TIS—small part, TIB—bone, TIC—cranial (see below): • General rule of thumb: TI never >3, TIC 4 mm in empty bladder), L length, W width, D depth. (b) Longitudinal (extended view technique is helpful in large-size bladders for proper measurement); (c, d) axial section—with axial measurements (callipers) for volume assessment; calculation depends on bladder shape that defines the correct correction factor: in spheric-ellipsoid shape factor = 0.5 (c), in a rectangular shape it is 1 (d). Note additionally thickened and trabeculated bladder wall. (e, f) Open bladder neck in axial (e) and sagittal (f) view—a potential sign for bladder instability or other functional disturbance. (g) Ureteric inflow jet–best seen on CDS: note the asymmetry in this example

• Assess: shape, size, position, contour, parenchymal echogenicity, and cortico-­ medullary differentiation, collecting system dilatation (if enlarged, measured in axial plane) and thickening of pelvic wall and peripelvic fat/fibrotic tissue. • Calculate renal volume (L × W × H × 0.53). • Assess vascular anatomy (CDS) (e.g. accessory renal artery); follow vessels to origin or drainage (e.g. retro-aortal left renal vein). Add spectral analysis if i­ndicated from main as well as intrarenal vessels (from upper, middle, and lower segment). • aCDS is applied for peripheral vasculature (e.g. focal perfusion defects?).

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Note  Physiologic difference in colour intensity between highly vascularised cortex and less vascularised medullae. Compare both sides in relation to perirenal structures. • Always assess perirenal space (adrenal gland). • Try to assess pelvi-ureteric junction (open? obstructed by vessel? kinking?…); follow ureter downwards, if dilated. • Assess collecting system after voiding (changes in dilatation?). • Consider CEUS for lesion characterisation (e.g. complicated cyst) or equivocal findings on baseline US/(a)CDS (e.g. suspected perfusion defects, traumatic lesions …). CDS  Document ureteric jet into bladder (symmetric? position of ostium?), vascular anatomy extrarenally as well as main intrarenal arteries (proper scale setting not to miss aliasing and turbulences at sites of possible stenosis or AVF…). Assess for possible twinkling (calcifications and sedimentations) (Fig. 15.2f), • New sensitive (a)CDS techniques (such as SMI) even better depict jets and “swirls”.

15.1.5.1 Diuretic US Used for assessment in dilated urinary tracts/distended pelvicalyceal system: standardised diuretic stress induced by medication (e.g. furosemide, dose = 1 mg/kg, up to 20 mg) given orally or IV (acts faster). Repeat assessment of kidney till findings (dilatation of collecting system, Doppler flow spectra) have returned to baseline— delayed or missing normalisation of flow patterns after diuretic stress indicates significant obstruction.

15.1.6 Contrast-Enhanced Voiding Urosonography (ce-VUS) Definition  ce-VUS = sonographic test for vesico-ureteric reflux (VUR). Has become a standard procedure for VUR evaluation since UCA approved for paediatric use. Is reliable, no radiation, can be performed at bedside (see also chapter on contrast-enhanced ultrasound). Short description outlined here, too. How To Do  After assuring sterile urine and initial US assessment performed, urethral catheter placed (or suprapubic puncture) and bladder emptied: • Then bladder gradually filled by drip infusion (infusion height 2–4  mm thick (depends less on age than on filling): • Ostium at latero-cranial end of bladder trigone as well as distal ureters often seen physiologically in well-filled bladder and good-hydrated children. • Assess bladder volume (see above and respective chapter). Simple equation often used to define normal range: volume (mL) = [age (in years) + 2] × 30. • Bladder neck closed unless there is an urge to void; after voiding bladder neck should be closed. Open bladder neck, thickened bladder wall, irregular inner contour with trabeculation and pseudo-diverticulae, high bladder tension, or atypical contour may raise suspicion of neurogenic bladder/functional disturbance.

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• For assessing retrovesical structures (distal ureter, retrovesical space, internal genitalia, etc.), adequate manipulation of TGC adaptation is necessary. Use ureteric jet for defining ostium position and assessing symmetry of urine inflow. Note  Nodular wall component at bladder roof may be physiologic as remnant of urachus. Furthermore in neonates the urachus may still be depicted for a couple of weeks but without patent lumen. In neonates with still immature bladder function, some residual urine does not indicate pathology.

15.2.2 Kidney Parenchymal appearance changes with age: • Neonatally—relatively thick parenchyma with accentuated cortico-medullary differentiation and rather echogenic cortex (may be as echogenic than adjacent liver tissue), with hypoechoic medullae. Distal medullae and papillae may exhibit echogenicities (transient physiologic phenomenon that resolves spontaneously) (Fig.  15.5). With age, cortico-medullary differentiation gets less pronounced; echogenicity of cortex decreases. Echogenicity of distal medulla becomes homogeneously hypoechoic (Fig. 15.6). • Sometimes papilla and pelvic wall become more echogenic with some slight echogenicity around central structures due to peripelvic fat and fibrosis. • Calices and renal pelvis may be visible, particularly with modern high-resolution transducers, without indicating urinary transport alteration (Fig. 15.7). • Assess fornices and papilla to demonstrate normal shape; assess renal pelvis wall (should not be thickened). In the hilum, the renal vein and artery are to be recognised and can be differentiated by following these structures to their vascular origin, whereas the pelvis curses downwards towards ureteropelvic junction. • Renal size: standardised measurements and volume calculation; compare with age-/weight-adapted growth charts (Table 15.1). Always compare to other side

Fig. 15.5  Normal neonatal kidney. (a) Longitudinal section of the right neonatal kidney with length measurement (+ …+). Note physiologically relatively high echogenicity of cortex (similar to liver), pronounced cortico-medullary differentiation and some (transient) echogenicity in distal medulla. (b) Axial section of the left kidney with measurements (callipers)—same appearance of parenchyma as in (a). (c) Axial section, neonatal left kidney: same parenchymal appearance as in (a, b) but some widening of renal pelvis (II°). Note  Dilatation best assessed after end of the first postnatal week—as physiological renal immaturity prevents filling of collapsed dilated system during first days of life. Standardised hydration essential for proper recognition and grading, particularly for follow-up investigations.

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Table. 15.3 (continued)

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US Findings Dilatation of pelvicalyceal system (PCD grade III°–V°)—lower grades usually associated with non-obstructive UPJA or lower grade VUR without thinning of parenchyma and preserved cortico-medullary differentiation. Ureteropelvic junction narrowed/not depictable; proximal ureter very narrow: • Pelvic ectasia: only pelvis dilated, calices visualised, but normal configuration, sometimes associated with non-obstructed ureteropelvic junction anomaly (UPJA). • PCD IV° (and V°) usually indicates high-grade PUJO (Fig. 15.17). • Signs for (chronically) decompensated obstruction: (severe) thinning of parenchyma, altered parenchymal echogenicity, lack of cortico-medullary differentiation, delayed or missing normalisation under diuretic stress by furosemide (diuretic urosonography). Potentially dysplastic cysts.

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Fig. 15.17  US in UPJO (including CDS). (a) Typical appearance of high-grade “hydronephrosis” (grade IV°) with significantly dilated collecting system, thinned parenchyma, and renal enlargement (+…+) in PUJO. (b) Cyst-like appearance of grossly enlarged collecting system (PCD V) in PUJO; peripheral rim-like parenchyma hardly visible but enables differentiation against MCDK (i.e. central parenchyma, no connections between cystic structures). (c) Axial section of mild PUJO with only little distension of calices and calyceal neck (1+ …+) and preserved parenchyma (2+…+) with persisting cortico-medullary differentiation (PCD grade III°). (d) Axial section: dilatation of extrarenal pelvis (+ +) but practically no dilatation of the intrarenal system. (e) Same patient as in (d) CDS reveals an additional renal artery crossing the pelvi-ureteric junction, possibly causing (intermittent) partial obstruction with dilatation of the renal pelvis. (f) Gross dilatation of collecting system and pelvis in severe, fetally decompensated PUJO. Echogenic, unstructured, and narrow parenchyma full with multiple cysts of different sizes (“obstructive dysplasia”). (g, h) Importance of hydration: kidney scanned in non-hydrated (g) and well-hydrated (h) state, the latter after furosemide-induced diuretic stress. Note significant change in dilatation of the renal pelvis (1+ +) and collecting system impressively demonstrating importance of proper patient preparation for US studies

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Note  Dilatation does not equal obstruction—US cannot diagnose obstruction. Even severe obstruction may show only minor distension under insufficient hydration/decreased function or with intermittent as well as per acute obstruction (e.g. urolithiasis). Diagnosis of severe/decompensated obstruction (which needs ­treatment to prevent deterioration of renal function/growth potential) relays on functional imaging. CDS Look for accessory/additional renal vessels that may impair ureteropelvic junction (Fig. 15.17): • In chronic and non-obstructive dilatation RI symmetric. • In acute obstruction asymmetric elevation of RI in affected kidney. • Also assess potential rarefaction of peripheral vascularity (sign of chronic decompensation with already reduced renal function/scarring), best visualised on aCDS. Postoperative transient thickening of pelvic wall, pelvis often smaller (as reduced by surgery) and dilatation of calices often persists for long time—only normalises over years, potentially focal perfusion impairment/scar (e.g. at site of perioperative drain). Note  For assessing split renal volume, the dilated collecting system has to be subtracted—best using 3DUS (allows segmentation of collecting system that can be deducted from overall renal volume, thus allowing exact parenchymal volume calculation—see respective chapters too). Can then be compared to non-obstructed contralateral side (= split/relative renal size). Additional Investigations MAG3 scintigraphy: gold standard for assessing renal function/urinary drainage. IVU: outdated—replaced by MRU, indicated in complex anatomy, particularly preoperatively • In some situations—particularly postoperatively—modified focused IVU helpful by assessing anatomy/obstruction (only need few well-timed focused images). Dynamic diuretic MRU: will in future allow for additional functional assessment. • No indication for CT, even accessory renal artery seen mostly by US/CDS and early angiographic phase of MRU. VCUG or ce-VUS: VUR assessment—particularly if indirect signs seen on US. • Postoperatively some perform fluoroscopic assessment of drainage before removing drain. Potentially replaceable by intracavitary ce-US (= install UCA in drain and observe drainage to bladder).

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Uretero-Vesical Junction Obstruction (UVJO)/Obstructive Megaureter (POM/MU) Definition Aetiology: stenosis at UVJ or regional dysplasia of ureter with lack of peristalsis, causing impaired urinary drainage. Potentially associated with anatomic changes at ostium (low insertion, ureterocele, ectopic ureteric insertion, duplex systems, etc.). US Findings Dilatation of ureter, more or less thickening of wall and varying impairment of peristalsis (can be documented by video clips/M-mode) (Fig. 15.18): • Hyperperistalsis indicates stenosis. • Lack of peristalsis hints at decompensation or dysplastic-atonic segment. • In complications (e.g. infection): echoes in ureter. Note  Dilatation of ureter does not necessarily correlate with dilatation of renal collecting system—associated kink/relative PUJO will increase intrarenal distension (PCD II°–V°).

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Fig. 15.18  POM/MU—M-mode. (a) Two cystiform structures depicted behind well-filled bladder lateral to uterus (proper TGC adaptation essential—automatic image optimisation programmes will not always work for this): to differentiate ovarian cysts from (bilateral) megaureter, longitudinal paramedian section is necessary. (b, c) Dilated ureter (+ +) behind well-filled urinary bladder in axial (b) and longitudinal (c) section; the latter nicely exhibiting short narrow distal/transmural section (obstructive megaureter). (d) M-mode documents lack of peristalsis in dysplastic widened ureteral segment (neonate with primary megaureter). (d) Significantly dilated renal collecting system in child with megaureter. Note cystiform fluid-filled structure below the lower pole of kidney (+ +) representing loop of tortuous megaureter. (e) Pelvi-ureteric junction has kink-like anatomy explaining intermittent secondary upper obstruction in addition to megaureter

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CDS No specific findings. Assessment of ureteric inflow jet may be helpful but potentially misleading. Improves depiction of ostium—thus identification of atypical insertion. Additional Investigations IVU replaced by (diuretic contrast-enhanced) MRU; for anatomic display T2-MRU. VCUG/ce-VUS for differentiation of dilating VUR. MAG3 scintigraphy—used for drainage assessment, split renal size, and function and assessment of ureteral peristalsis (or dynamic MRU). Posterior Urethral Valve (PUV) Definition Most common in baby boys. Has a number of forms. Severe distal obstruction often associated with upper tract pathology—high probability of congenital renal dysplasia and chronic renal failure. US Findings • Thickened bladder wall, trabeculation, (pseudo-)diverticula, enlarged capacity, typical valve-like configuration of bladder neck (particularly well seen by perineal US during voiding attempts) (Fig. 15.19). • Secondary high-grade VUR or obstruction by thickened bladder wall, associated with more or less renal dysplasia, dilation of collecting system, potentially pop-­ off urinoma (Fig. 15.20)—the latter will prevent kidney from further damage. This can also occur in other scenarios (e.g. obstructing ureterocele) (Fig 15.20e). CDS Demonstrates renal perfusion; helps assessment of severely dysfunctional kidneys. ce-VUS may show valve (perineal approach during voiding); VUR may show pop-off urinoma. DDx • Prune belly syndrome (hypoplastic abdominal wall, cryptorchidism, hypoplastic prostate, hypoplasia of posterior urethra, commonly associated with complex urinary tract anomalies/dilated ureters with less-dilated intrarenal collecting system and dysplastic parenchyma). • Neurogenic bladder. • High-grade VUR. Additional Investigations • Initial confirmation by VCUG recommended. • Early urinary drainage either by bladder relief or nephrostomy.

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Fig. 15.19  US in posterior urethral valve (PUV). (a) Longitudinal section of large bladder with impressive wall thickening and obstruction of ureteral ostium (arrow) in baby with PUV. (b) Cross section through wall-thickened urinary bladder (after drainage via catheter) shows dilated ureter behind bladder and trabeculation. (c) Normal perineal US in baby boy (no voiding). (d) Perineal US, neonate: open bladder neck and proximal urethra to pelvic floor when trying to void—not to be confused with PUV (as on VCUG). (e) Normal male urethra during voiding on ce-US. (f) Typical valve configuration of PUV on perineal US during voiding. (g) ce-VUS: valve-like urethra configuration nicely demonstrated during voiding; catheter only seen in basic image, contrast agent better visualised in left, dedicated contrast-specific image. (h) Para-ureteric cyst (*) seen on perineal US with no connection to urethra. (i) Ureteric duplication posing as a diverticulum (*) with some sort of ureteric stenosis (incomplete valve/ureteric fold) depicted by retrograde US-urethrography (arrow = catheter for US-urethrography using saline)

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Fig. 15.20  Pop-off urinoma with renal dysplasia. (a) Dysplastic kidney in neonate with PUV, dilated pelvis, and dysplastic cysts. (b) Complex fluid formation adjacent to relatively normal looking kidney in PUV, consistent with calyceal rupture and pop-off urinoma which seems to have a protective effect reducing renal damage. (c) Same neonate as in (b): good vascularisation of renal parenchyma, large urinoma in front of kidney. (d) Dual/split image technique, dorsal axial scan through both kidneys including aCDS: obviously significant difference in renal size and perfusion, left kidney severely damaged (same can also be seen in other patients with high-grade VUR without PUV) (e) Urinoma of right duplex kidney in a baby with ureterocele (*) (f), also obstructing bladder outlet which is best seen in a perineal view (g) and not just the respective upper moiety— after rupture of the upper moiety’s calix (arrow)

• Renal function assessed by DMSA scintigraphy (best results after approx. Third month of life—as it only works with sufficient renal function after renal immaturity has ceased). • Rarely MRU (in additional complex pathology). • No indication for IVU. Vesico-Ureteric Reflux (VUR) Definition Insufficient urinary ostia (primary/secondary); reflux of urine from bladder to ureter/renal collecting system—with more or less dilatation of ureter and/or calyceal system. Grading I°–V° according to international classification.

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US Findings Indirect signs in bladder: bladder wall thickening, trabeculation, lateralisation of ostium, and gaping ostium. Varying dilatation of ureter that may exhibit wall thickening. Post-void increase of dilatation of collecting system and pelvic urothelial thickening (Fig.15.21). CDS Ureteric inflow jet may be atypical, asymmetric, and originate from lateralised ostium.

Fig. 15.21  Vesico-ureteric reflux. (a) Left kidney, axial view before voiding: no distension of collecting system/renal pelvis. (b) Same girl, same section after voiding: significant widening of the renal pelvis indicating dilating VUR. (c) Urothelial sign: thickened wall of non-distended renal pelvis—a nonspecific sign for VUR, involvement in UTI, obstruction, congestions, etc. (d) Duplex ureter—the upper and more lateralised ostium (draining lower moiety of respective kidney) is gapping, indicative of VUR. (e) ce-VUS shows contrast reflux into proximal ureter and renal collecting system. (f) Comparison of two kidneys in same patient showing different size and pelvic wall thickening associated with different degree of VUR

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Sometimes, particularly with particles in urine, VUR can be directly visualised by reversed colour flow signals in ureter. Note  These have to originate from within bladder through ostium—as otherwise reflected retrograde flow from closed ostium may mimic VUR. ce-VUS (see also respective entry and chapter): reflux of US contrast agent into ureter/pelvicalyceal system—with more or less distension, depending on VUR grade. Grading of VUR achievable by ce-VUS (correlates with standard VUR grading on VCUG). Note  Always assess renal parenchyma for signs of dysplasia/scars after infections. Connatal dysplasia in severe VUR (common in baby boys, PUV) called “congenital reflux nephropathy.” Postnatally VUR itself does not cause renal damage, only in conjunction with recurrent upper UTI. Additional Investigations VCUG—particularly in boys, preoperatively, for detailed analysis not only of urethra (also ureter, potential diverticula…). Rarely bladder function studies are performed. DMSA scintigraphy for assessing renal parenchyma damage (might be replaced by MR in future). IVU outdated. Secondary Obstruction Definition Number of causes such as urolithiasis or compression (by tumours, retroperitoneal fibrosis, etc.). US Findings Acute obstruction usually does usually not exhibit significant dilatation—unless there is preexisting chronic drainage impairment/other forms of dilatation. Increased echogenicity of parenchyma and swollen and enlarged kidney. Potentially perirenal oedema/stranding. Concretions/stones (urolithiasis): usually echogenic structure with dorsal shadowing, distended collecting system or ureter narrows after level of obstruction. CDS In acute severe obstruction, there is diminished peripheral vasculature (a) CDS. Asymmetrically elevated RI in acutely obstructed kidney.

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In total obstruction, lack of ureteric inflow jet from affected ureter—otherwise asymmetric (even ipsilateral dominant) ureteric jet (e.g. from haematuria). Twinkling sign from stone (Fig. 15.22). Role of US Perfect initial diagnostic tool: • In children, stones can be visualised in nearly all parts of urinary tract, particularly in kidney, at pelvi-ureteric junction, in distal ureter—provided sufficiently filled bladder allows access. Even urethra (by perineal US) (Fig. 15.22d). Note  Following dilated ureter downwards from renal pelvis will often allow depiction of obstructing stone even in mid/lower ureter, e.g. at pelvic vessel crossing. Furthermore initial US allows tailoring of further examinations. Adjacent compressing structures can usually be visualised, too; potential for US-guided intervention.

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Fig. 15.22  Twinkling sign/ureteric stone. (a) Distal ureteric stone (1+ …+) with some dilatation of ureter and only little shadowing, only depictable with sufficiently filled urinary bladder. (b) Urethral stone (1+ …+) depicted by perineal US. (c) Twinkling sign caused by urethral stone (same patient as b). (d) Pelvic floor rhabdomyosarcoma, visualised through bladder (2+  …+) compresses + displaces urethra (U, 1+ …+), causing urethral obstruction

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Additional Investigations • Kidney-ureter-bladder film (KUB). • Focused IVU or stone CT (particularly in complex and equivocal situation where it is increasingly preferred): –– Not indicated with same frequency as in adults—due to radiation burden. • Role of MR is yet undefined. • See also ESPR/ESUR recommendations—Pediatr Radiol (2010) 40:1315.

15.3.2 Inflammatory Renal Parenchymal Conditions Role of US Perfect initial diagnostic imaging method and for follow-up (and US-guided biopsy for DDx). Additional Imaging DMSA scintigraphy in acute or chronic setting (for scars, wait 4–6  months after infection): • Complicated infections or DDx of pseudotumours may require MR (or CT, if MR is not available). • IVU usually not indicated in children (rare exceptions, e.g. unless there is a suspected obstructing stone). • Additional nephro-urologic work-up of potentially underlying/associated condition recommended. • Imaging algorithm for paediatric UTI: see ESPR/ESUR recommendation Pediatr Radiol (2008) 38:138.

15.3.2.1 Pyelitis Definition In children isolated pyelitis is rare—potentially associated with VUR. Commonly associated with interstitial bacterial nephritis. US Findings Thickened echogenic renal pelvic wall and echoes within collecting system, which tends to be enlarged, hypotonic, and wide (Fig. 15.23). Secondary stone formation or fungus may be present; fungus usually similar to a stone, often larger and somewhat polygonal shaped; dorsal shadowing less than with a typical concretion, may cause secondary obstruction.

15.3.2.2 Acute Pyelonephritis (aPN)/Interstitial Nephritis Definition Haematogenous or ascending infection, bacterial or viral, sometimes atypical (tuberculosis).

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Fig. 15.23  US in urinary tract infection (UTI). (a) Echogenic content floating throughout bladder in UTI. (b) Echogenic debris (clot and fibrin) sitting at bladder base in haemorrhagic cystitis. (c) Enlarged kidney, with swollen urothelium of lax and slightly distended renal pelvis in an infant with upper UTI (acute pyelonephritis). (d) Enlarged kidney with disrupted cortico-medullary differentiation and increased echogenicity in upper UTI with diffuse renal involvement. (e) aCDS depicts multi-segmental perfusion defects in same child as (d); these local manifestations were less depictable on gray scale US

US/CDS Findings Focal/diffusely altered parenchymal echogenicity—commonly increased, swollen kidney, in focal infection even pseudotumours, regional swelling (“lobar nephronia”), peripelvic increased/broadened echogenicity and perirenal oedema, often associated with findings as in pyelitis. Regionally/segmentally decreased vascularity—particularly well seen on aCDS, diffuse asymmetrically reduced vascularity on power Doppler in diffuse infection (Fig. 15.23).

15.3.2.3 Necrosis and Abscess Formation US/CDS Findings Increasingly inhomogeneous defect, hypoechoic structural alteration with eventually complex cystic configuration and rim-like margin; may resemble complicated cyst. Focal perfusion defect, potentially capsular hyperaemia (Fig. 15.24); CEUS may enhance depiction and aid DDx.

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Fig. 15.24  Complications in UTI, DDx, scarring. (a) Focal necrotic cortical area (+ …+) seen as hypoechoic spheric lesion in severely prolonged upper UTI; note also broadened peripyelonal echogenicity and hazy cortico-medullary differentiation of swollen kidney. (b) Multiple necrotic (dark) segmental defects throughout kidney in severe diffuse/multifocal necrotising pyelonephritis. (c) Same patient as in (b): aCDS demonstrates only minimal residual central perfusion—eventually entire kidney had to be removed. (d) Spheric focal complex liquid lesion in a child after UTI, with sparing of vessels on aCDS–consistent with early appearance in formation of an renal abscess

15.3.2.4 Scarring US/aCDS Findings • Regional narrowing of parenchyma with contour alteration, disrupted/abnormal cortico-medullary differentiation, and clubbing of affected calix. • Regional small strip-like defect, particularly well seen on aCDS (Fig. 15.25).

15.3.2.5 Tuberculosis US/CDS Findings Necrosis/atypical abscess—echogenic content, potentially with partial rim-like calcifications, commonly similar as complicated cyst. No other specific US/aCDS findings. 15.3.2.6 Xanthogranulomatous Pyelonephritis Definition Chronic infection, often with obstructive concretion/stone (“staghorn” shaped) that leads to destruction of medulla, eventually of entire kidney. US/CDS Findings Regionally or diffusely thinned parenchyma and vasculature (aCDS), peripheral hyperaemia in membrane around abscess formation. Pseudotumourous aspect of

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Fig. 15.25  Scarring. (a) Focal scar with clubbed calyx and destroyed cortex after the upper pole aPN. (b) Small peripheral scar (+ +) seen as perfusion defect on aCDS, not easily depictable by gray scale US

Fig. 15.26  Xanthogranulomatous pyelonephritis. Xanthogranulomatous pyelonephritis in a child with distal renal acidosis and stone disease, longitudinal (a) and axial (b) section: complex cystic destruction of medullae, central calcifications, tumourously enlarged kidney, shape somewhat preserved

destroyed affected part. Disruption of normal renal parenchymal and vascular architecture in abscess and necrosis; potentially perifocal hyperaemia around kidney (Fig.15.26).

15.3.2.7 Glomerulonephritis/Nephrotic Syndrome Definition Large range of conditions. US Findings Commonly increased renal size, small medulla, enlarged cortex, and potentially increased echogenicity/reduced cortico-medullary differentiation, depending on which compartments involved (Fig. 15.27).

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Fig. 15.27  Glomerulonephritis. (a) Swollen large right kidney (+  +) with small hypoechoic medullae in acute but mild (postinfectious) GN (findings bilateral, renal function normal). (b) A less-enlarged but still slightly swollen kidney with hyperechoic parenchyma and reduced cortico-­ medullary differentiation in chronic recurrent GN (HUS may appear similar)

Typically bilateral findings: • • • •

In chronic stage, kidneys may be small. In mild/atypical disease, kidney may look normal. Differentiation between various entities sonographically impossible. Other systemic findings: ascites, pleural effusion—depend on degree of renal failure/associated condition.

Consider renal manifestation of systemic disease such as lupus, Henoch– Schonlein purpura, amyloidosis, familiar Mediterranean fever, etc. CDS Findings Diffuse perfusion alterations—correlate more with degree of renal failure than with underlying entity (except for primarily vascular conditions—see below). Role of US Initial diagnosis: exclude other conditions by validating pre-/postrenal causes of renal failure. Assessment of renal perfusion, also during course of disease, as well as secondary/associated changes (e.g. under haemofiltration—intravascular volume?). US-guided biopsy for histological evaluation (see respective chapter too).

15.3.3 Vascular Conditions Role of US in Renal Vascular Conditions Most developed tool for screening, initial diagnosis, and follow-up. US most useful for follow-up, differentiation against other renal conditions, and monitoring of future renal growth.

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Will allow depiction of changes in perfusion patterns: • However, if US potentially limited, then additional imaging necessary (see above). • Algorithms recommended for certain conditions, e.g. imaging in suspected childhood renovascular hypertension (see Pediatr Radiol (2010) 40:1315).

15.3.3.1 Renal Artery Stenosis Definition Rare in childhood, commonly not arteriosclerotic in origin but associated with other vasculopathies, after vasculitis, trauma/surgery, by compression. US Findings • Using meticulous scanning techniques, entire course of extrarenal artery is often visualised. • Rarely changes in diameter or aneurysmal dilatation seen on gray scale. • Intrarenal portions only assessable using CDS. CDS • Most striking finding: aliasing of colour spectrum—provided adequate scale settings. • Always perform spectral analysis: –– At level of stenosis: marked increase in systolic velocity with spectral broadening + turbulent flow. –– Distal to stenosis: decreased systolic velocity, more or less normal to elevated diastolic velocity, depending on severity/grade. Delayed systolic upstroke with increased acceleration index (pulsus tardus et parvus) (Fig. 15.28). –– In kidney: sometimes aCDS depicts segmental hypoperfusion due to infarction of affected area after severe stenosis.

Fig. 15.28  Renal artery stenosis. Elevated flow velocity with turbulent atypical flow at site of the left renal artery stenosis, also seen as aliasing of CDS signals and narrow vessel diameter. Note that at stenosis no flattening of systolic upstroke may be present in the spectral Doppler trace

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Note  Always assess all renal sectors (as in children intrarenal stenosis quite common)—peripheral and main segmental branches need to be seen on CDS for reliable assessment. Always assess abdominal aorta/other low-resistive flow vessels (e.g. coeliac trunk, cerebral vessels) to differentiate focal from systemic conditions. Remember, that particularly in gray scale dissection may be hard to see; US does not always allow exclusion of stenosis. In some conditions ce-US can enhance US potential. Additional Imaging Captopril scintigraphy. CT/MR angiography and catheter angiography with PTA/stenting.

15.3.3.2 Arteriovenous Fistula (AVF) Definition Rarely spontaneous or idiopathic (vasculopathies), common after surgery, trauma, biopsy. US Findings Large fistula may show as cystic interruption of normal renal parenchymal structure. Secondary sedimentation in renal pelvis due to haemorrhage. Cortical infarct of dependent area. CDS Most useful tool for depicting AVF. • Adapt scale to become sensitive for aliasing (demonstrates site of AVF). • Feeding artery hyperaemic with increased velocities/low RI; draining vein may have increased velocities with arterialised flow spectrum—spectral analysis mandatory (see Fig. 15.35). • At AVF: unidirectional high-velocity turbulent flow. • aCDS visualises focal peripheral perfusion impairment of dependent areas—risk of infarction. Additional Imaging ce-CT/MRA. Catheter angiography—potentially with embolisation.

15.3.3.3 Infarction Definition Rare in childhood—posttraumatic, postoperative, postinterventional, in coagulopathies, other systemic disease such as haemolytic anaemia (e.g. sickle-cell anaemia). US Findings Initially difficult to differentiate from focal pyelonephritis but soon develops increasingly sharp borders with triangular shape and rather echogenic parenchyma (Fig. 15.29).

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Fig. 15.29  Renal infarction. (a) Echogenic, more or less triangular-shaped segmental parenchymal lesion in a child with sickle-cell anaemia, consistent with an infarction. (b) No vessels depictable by aCDS in this traumatic renal infarction of parts of the kidney (dissection of supplying accessory artery). (c) Polar infarction (+ +) demonstrated by aCDS after sacrificing a polar artery during transplantation

Eventually (necrosis) less echogenic, develop into scars—cannot be differentiated from other scars. aCDS Segmental perfusion defect; detection can be enhanced by intravenous ce-US. Additional Imaging Only if of therapeutic consequence: ce-CT/MRI. Potentially scintigraphy.

15.3.3.4 Renal Vein Thrombosis Definition Rare, but exists even in neonates: • Causes: posttraumatic, postoperatively, postinterventional, coagulopathies, dehydration, systemic infection, tumourous/by local compression/displacement (e.g. after neonatal adrenal gland haemorrhage with displacement of kidney—in this condition always assess renal perfusion!). • May often start peripherally, eventually grows into central veins—in early stages central renal vein may be patent. • Tumour thrombus (particularly Wilms tumour) may grow through renal vein into IVC, up to right atrium. Risk of pulmonary embolism. US Findings • In central vein or IVC, thrombus formation is visualised replacing normal anechoic lumen of then often distended vessel. • Most striking—secondary changes in the kidney: swollen, echogenic (regionally pronounced  =  haemorrhage) and with disrupted cortico-medullary differentiation (Fig. 15.30). • Intrarenal thrombus cannot be visualised directly.

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Fig. 15.30  Renal vein thrombosis—typical US and CDS findings. (a) Echogenic swollen kidney in neonate with haematuria. (b) CDS with spectral trace exhibits high-resistance arterial flow; no venous flow depictable. (c) Renal vein thrombus reaches into IVC

CDS • Striking hypovascularisation of affected area/kidney; non-affected parts/central vessel may still exhibit antegrade flow (often with bidirectional colour flow signals) (Fig. 15.30). • Spectral trace in affected area—bidirectional arterial flow with short high-peak systolic inflow and diastolic backflow, which drains all systolic blood flow (no effective antegrade perfusion). • No venous colour signals/flow spectra depicted in affected area/vein(s). Role of US In combination with clinical symptoms and signs, the typical US and CDS findings are diagnostic; no additional imaging needed or will reveal additional information. Even in tumour thrombus, CDS is the most sensitive method; otherwise for assessment of thrombus of IVC, contrast-enhanced sectional imaging may be used.

15.3.4 Nephrocalcinosis Definition Precipitation of echogenic, calcium containing material at cortico-medullary junction, tubules/papillae, cortex…. Various causes: hypercalciuria, distal renal acidosis, Bartter syndrome, oxalosis, secondary to other diseases (e.g. sickle-cell anaemia/sickle-cell nephropathy). US = major imaging tool. US Findings Sonographically medullary nephrocalcinosis exhibits three stages (Fig. 15.31): • Stage I: initially echogenic cortico-medullary transition zone. • Stage II: increasing peripheral medullar echogenicity, increasing echogenicity of papilla—eventually entire medulla echogenic. DDx of latter: remnant of papillary necrosis.

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Fig. 15.31  Nephrocalcinosis. (a) Echogenic depositions in distal tubules close to papillae in a neonate after furosemide therapy. (b) Echogenic outer layer of medulla in early (stage I) medullary nephrocalcinosis. (c) Entire medullae calcified, with shadowing—late stage of medullary nephrocalcinosis (stage III), but cortex is preserved (no global calcinosis)—kidney borders difficult to depict, outlined (+ +1, 2)

• Stage III: entire medulla calcified; finally also cortical deposits—increasing echogenicity of the entire kidney. Note  Commonly nephrocalcinosis starts at medulla, not to be confused with physiologic transient medullary/papillary echogenicity of neonates (transient, resolves spontaneously). Cortical forms initially cause increasing echogenicity of cortex (e.g. overdose of Vitamin D). Global nephrocalcinosis of cortex  +  medulla extremely rare in childhood, often late stage of systemic disease, with additional urolithiasis/papillary necrosis, etc. CDS Twinkling sign—particularly in more advanced forms. Role of US • • • •

Mainstay of imaging. Depicts findings in early stage (still negative on plain film). Also used for follow-up. CT will also show deposit but not used due to radiation burden.

DDx Similar gray scale findings in atypical manifestation of congenital nephrotic syndrome of Finnish type, ARPKD, renal vein thrombosis, cystinosis, oxalosis, glycogenosis, and tyrosinemia—these conditions must particularly be considered with atypical manifestation, visualising of other signs (e.g. tubular ectasia) and very early manifestation. Can eventually also lead to calcification of papillae (papillary calcinosis) and urolithiasis.

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Fig. 15.32  Urolithiasis. (a) Stone with shadowing in proximal ureter/pelvi-ureteric junction. Kidney enlarged (+ …+) and hyperechoic in acute obstruction by urolithiasis; some dilatation due to recurrent episodes larger than usually seen in single acute event. (b) Same patient as in (a): subtle twinkling of stone—not all stones exhibit vivid twinkling. (c) Stone (1+ …+) with shadowing in mid-ureter—note change of calibre of ureter due to obstruction; ureter visible by using graded compression following psoas muscle. (d) The twinkling sign depicts stone in proximal ureter, hard to see on gray scale US (little shadowing and only slight distension of collecting system). Kidney swollen, hyperechoic, with vague cortico-medullary differentiation in peri-acute stage

15.3.5 Urolithiasis Definition Less frequent in children than in adults—varying geographic distribution. Number of underlying metabolic conditions to be considered. Details of US appearance/value of additional imaging are partially described above (nephrocalcinosis), partially illustrated in Fig. 15.32. Most stones can in childhood be depicted sonographically—thus “stone-CT” is rely needed in childhood and should be avoided for radiation issues (particularly as stone disease often is a life-long condition that will cause many repetitive CTs later on in adulthood, and radiation burden will add up over time to considerable doses!). However, a full bladder and meticulous scanning is essential for not missing particularly distal ureteric stones. US/CDS/Doppler Findings (Fig 15.32) Stone can be more or less echogenic, depending on the composition • Often with shadowing—but not always Kidney enlarged/swollen.

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Parenchyma hyperechoic in acute obstruction/(hyper-)acute stage, with vague cortico-medullary differentiation Little dilatation of pelvi-caliceal system in acute event • More distention in recurrent episodes or with preexisting dilatation Twinkling sign on CDS, but not all stones exhibit vivid twinkling. • May help to depict stones (e.g. in non-dilated proximal ureter) which are hard to see on gray scale US Asymmetrically elevated RI in affected kidney (in acute stage) • Will gradually normalize over time even if stone not resolved (as in obstructive uropathy—see respective entry) Usually stones sit at pelvi-ureteric junction or distal ureter just before ureterovesical junction, then easily accessible in most (pediatric) patients • Sometimes different locations (e.g. pelvic vessel crossing)—the latter approachable by gradually following the slightly distended proximal ureter without too much compression to the level pelvic entry. These stones sit close to common iliac vessels and next to the iliopsoas muscle—then often the caliber change and the echogenic twinkling stone can be visualized Bladder inflow jet (best seen by CDS) may be missing or asymmetric • Sometimes stronger on affected side due to erythrocytes as strong reflectors in urine from affected side thus increasing color signals Tip  If some echogenicities cannot be properly located, try positioning maneuvers to differentiate papillar or wall calcifications/structures from intraluminal floating stones that move when repositioned. Note  Do not confuse physiologic conditions with stones or nephrocalcinosis—e.g. the physiologically echogenic papilla of the newborn that also may even cause twinkling, air in the system (e.g. after surgery or intervention or if refluxing after catherization), or e.g. fungus balls US used for follow-up, but remnants of urolithiasis after lithotripsy will appear different as the original stone. With increase in nephrocalcinosis, visualisation of urolithiasis within collecting system and differentiation of urolithiasis versus papillary calcinosis will become difficult.

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Additional Imaging Abdominal plain film (KBU)—in some places still standard in imaging urolithiasis, • May be necessary for deciding on treatment or guiding percutaneous shock wave lithotripsy IVU (intravenous urography) in general practically outdated—only sometimes, in special cases, focused IVU with selected images and timing may be the easiest and only available problem-solving tool • Particularly in (e.g. remote) areas with restricted access to dedicated pediatric imaging In children rarely unenhanced (low dose) stone CT indicated (reasoning see above) Mostly used as problem-solving tool in equivocal cases • And in patients not suitable for US (e.g. obesity, spine malformations with distorted habitus and lacking sonographic access, etc.) MRI not well established for this query and also has restricted potential

15.3.6 Other Important Renal Parenchymal Disease 15.3.6.1 Haemolytic Uremic Syndrome (HUS) Definition Complication of bacterial enterocolitis; haemolysis congests renal vessels—causes renal failure. US Findings Initially bilateral enlarged hyperechoic kidneys with small anechoic medullae. Three stages differentiated: • I: increased cortical echogenicity in relation to adjacent liver. • II: even more increased echogenicity—still small hypoechoic medullae visible. • III: completely hyperechoic kidney without cortico-medullary differentiation; always associated with complete renal failure. Further development depends on course of disease—from stepwise normalisation to cirrhotic kidneys with chronic renal failure (CRF).

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CDS • Nonspecific but helps to find vessels for spectral analysis. • Signs of increased resistance with low/inverted diastole, high systolic flow, and increased RI. • Reduced venous flow. Note  Doppler nonspecific. Always assess other vessels for comparison (renal versus systemic/cardiac condition). Tip  Spectral analysis may help predict prognosis—perfusion patterns normalise prior to normalisation of creatinine on blood samples, helpful in planning ongoing dialysis. Additional Investigation • Always assess entire abdomen—confirm diagnosis of enterocolitis. • Search for ascites/other complications. • Eventually—in unclear cases/prognostic reasons—US-guided renal biopsy (provided normal coagulation). • No other imaging performed.

15.3.6.2 Glomerulonephritis/Nephrotic Syndrome See above. 15.3.6.3 Scars, Cirrhotic Kidney Remnants or residual of previous disease. Cirrhotic kidney always associated with severe loss of renal function. If other kidney healthy—contralateral hypertrophy (volume calculations essential). Focal scars: usually after trauma or infection and infarction, defined by parenchymal narrowing, calyceal clubbing, altered echogenicity, and cortico-medullary differentiation—also see above. Focal hypertrophy—hypertrophic Bertin columns. US/CDS Findings • Diffusely/focal altered echogenicity, variably clubbed calyceal system. • Commonly increased echogenicity with reduced cortico-medullary differentiation. • Focal or diffuse reduced vasculature—however, RI may be normal. Additional Investigations • DMSA scintigraphy for split renal function (results with function 10%/>20 mL). • Physiologically residual urine noted in neonates (immature bladder function) and after nonphysiological voiding situations. Ureteric inflow may be seen on gray scale, particularly if urine very concentrated of with cellular content: • CDS will improve depiction of ureteric jet, which usually should be symmetric and regular—helps depiction of asymmetric ostium position or asymmetric urine inflow (see Fig. 15.2). Note  All respective sections have to be documented.

15.7.2 Pathologic Findings 15.7.2.1 Atypical Shape (Neurogenic Bladder, “Valve Bladder”) Nonphysiologic tension even with little filling, volume, signs of dysfunction (open bladder neck), thickened trigone, thickened bladder wall, reduced/enlarged capacity, trabeculation, pseudo-diverticula; atypical position/number/shape of ostium (e.g. gapping ostium), etc. (Fig. 15.42): • (Secondary?) Dilatation of distal ureter with stenosis by thickened bladder wall, ureteral junction stenosis (obstructive megaureter—UVJ obstruction, see below), dysplastic/immotile segments, obstructing concretions

15.7.2.2 Polyps Arising from the wall or entering through bladder neck (urethral fibroepithelial polyps). May exhibit central vessel arising from the bladder wall (Fig. 15.43). 15.7.2.3 Bladder Tumours Rare in children. Either diffusely infiltrating wall with wall thickening (e.g. neurofibroma), arising from wall/growing into lumen or into paravesical space in cauliflower-like appearance (mostly rhabdomyosarcoma) or also arise from adjacent structures infiltrating bladder (e.g. from prostate/vagina). US nonspecific may exhibit vascularity (Fig. 15.44). DDx: clots/fibrin (may be adherent to wall, then positioning manoeuvres do not help for differentiation, as they then do not change position), pseudotumours in atypical or haemorrhagic infection, polyps.

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Fig. 15.43  Bladder polyps. (a, b) Typical polyps of bladder wall (+ +) with typical vascular pedicle depictable by aCDS (a) or CDS (b). Bl bladder. (c) Polypoid structure (+ +) reaching into the bladder through bladder neck, in a child with a fibroid polyp of the posterior urethra

Fig. 15.44  Bladder wall (pseudo)tumours and DDx. (a) Bladder rhabdomyosarcoma: cauliflower-­ like polypoid tumour growing into bladder lumen, with broad attachment to the bladder wall. (b) Regional thickening of the bladder wall in a child with neurofibromatosis Type I, consistent with bladder wall neurofibroma (+ +) Fig. 15.45  Bladder wall calcification. Echogenic inner layer of thickened bladder wall in amoebiasis

15.7.2.4 Calcification in/of Bladder Typically in advanced schistosomiasis—with an echogenic layer in thickened bladder wall, usually with reduced bladder capacity/increased bladder tension (Fig.  15.45). Also urolithiasis may occur in bladder after passing from above or (infectious) stones grow in bladder (e.g. after / during infection, in cystinuria…). DDx: thickening of bladder endothelium in inflammation (cystitis) with free-­ floating particles in lumen, bladder sedimentation (blood, proteins, cells,

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concentrated urine, crystals, concretions—particularly large stones in oxaluria/cystinuria, etc.).

15.7.2.5 Ureterocele Cystiform end of ureter protruding into the bladder lumen at ostium: • Orthotopic ureterocele usually draining single renal system, central opening. • If associated with duplex kidney, then typically positioned at more distal-medial position entering ureter that drains the upper moiety of duplex system, often causing megaureter. Usually have opening at mediocaudal aspect of ureterocele. US/CDS Findings • Cystic structure protruding into the bladder of varying size. • Large ureteroceles may herniate into the bladder neck causing obstruction during voiding (Fig. 15.46). May also drain ectopically, protrude into vagina or paravesically/proximal ureter, seminal vesicles, etc.

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Fig. 15.46  Ureterocele. (a) Typical image of a ureterocele protruding into the bladder lumen like a cyst at site of the ostium. (b) Parasagittal oblique section through ureterocele depicts corresponding megaureter (+ +) behind bladder. (c) Small collapsed ureterocele in an insufficiently hydrated child—only some ostial irregularity and thick wall of ureterocele (+ +) depictable by meticulous scanning. (d) Ectopic ureterocele (1+ …+) behind bladder, potentially draining into vagina or urethra. (e, f) ce-VUS in a duplex kidney with ureterocele: observe non-contrasted ureterocele (UC) with respective megaureter (MU) (e), contrast reflux into the other dilated ureter (U) up to grossly dilated lower moiety (f, oblique section)

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• Urine inflow jet depictable by CDS—helps differentiating ectopic versus orthotopic ureterocele and assessing degree of obstruction/patency. Note  (Small) Ureteroceles may collapse with poor diuresis—sufficient bladder filling, observation over some time during peristaltic wave, and sufficient hydration essential not to miss e.g. small ureteroceles. May also evert forming a—diverticulum with increased intravesical pressure (e.g. full bladder, during voiding)—then respective ureter may become refluxing.

15.7.2.6 Persisting Urachus Foetal remnant, physiologically seen in first weeks of life, usually regresses. Considered pathologic if with central lumen that drains bladder to umbilicus, or persisting into infancy/childhood. Different forms: cyst or ducts. US Findings String-like structure seen even with poor bladder filling using high-resolution linear transducers, coursing in midline close to the abdominal wall, from bladder roof to umbilicus (Fig. 15.47). For assessment of patency and lumen, good bladder filling essential: • Potentially need to fill bladder with saline and/or UCA (as done for fluoroscopy), or also by careful injection of umbilical opening. Remnants of urachus may persist in form of urachal cyst/diverticula—may get infected, seen as complex cystic/abscess-like structure along course of the urachus. Note  Physiological remnant of the urachus may cause pseudotumourous nodule in the bladder wall at bladder roof—physiologic, should not be mistaken for bladder tumour.

Fig. 15.47  Urachus. (a, b) Typical appearance of band-like structure (+ +) connecting bladder roof to umbilicus. Close-up (a) and overview (b); no lumen visualised—however this may be missed with poor bladder filling. (c) Axial section through full bladder: tumour-like nodule in the bladder wall on bladder roof, consistent with a physiological urachal remnant—not to be mistaken for tumour

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15.7.2.7 Megaureter Dilatation of distal ureter, varying dilatation in the middle/proximal portion. Can be obstructive (stenotic uretero-vesical junction—uretero-vesical junction obstruction—UVJO), refluxive (high-grade dilating reflux with gapping ostium and changing size), or dysplastic (primary megaureter) with dysplastic segment which has less muscle and no peristalsis. US Findings Dilated ureter, with/without peristalsis; often with some thickening of the urothelium/ureteral wall. Try to always find ostium (often associated with slightly altered position, commonly more medially and distally in obstructive types, more lateralised and cranially in refluxive types). Always assess tortuosity, peristalsis (documentation with M-Mode/cine-loop clips helpful) as well as varying dilatation of the renal collecting system. May be associated with duplex kidneys (see Figs. 15.10 and 15.18). Note  For depicting and evaluating megaureters (initially and follow-up), standardised hydration/sufficiently filled bladder mandatory.

15.7.2.8 Infravesical Obstruction and Urethra Most commonly posterior urethral valve (PUV, nearly always in baby boys). Other forms of infravesical obstructions may be strictures and stenosis (rare), partial valves/folds, concretions, tumours (arising from prostate or pelvic floor), urethral malformations (diverticula, duplex urethra, severe hypospadias, etc.). Rarely fistulae may exist—difficult to visualise on US. US Findings Suspected by indirect signs (bladder wall thickening, open bladder neck, trabeculation, megaureters, etc.). Directly visualised on perineal/penile US with open bladder neck, particularly during/attempts of voiding—shows typical dilatation of the posterior urethra in PUV (or tumour/site of compression) (see Figs. 15.19 and 15.22). Other urethral and paraurethal pathology can be depicted by US such as paraurethral cysts, urethral dublication or diverticula, etc…—only if assessed during voiding or when urethra is filled retrogradely via catheter (US-urethrography, see ESPR Task force recommendation, Pediatr Radiol 47, 2017), possibly using a step-by-step pull-back manoeuvre as known from fluoroscopy (Fig. 15.19). Some findings can be enhanced by 3D/4DUS. Note  ce-VUS/perineal US can usually reliably depict PUVs when assessed during voiding.

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Additional Investigations VCUG/urethrography, cystourethroscopy. For tumours (in future?) MR urethrography.

15.7.2.9 Inflammation Isolated cystitis or part of UTI involving also upper tract(s). US/CDS Findings More or less thickened bladder wall, particular inner mucosal layer. Echoes within lumen: • Potentially widening and laxity of ureters, with urothelial sign (wall thickening). • Hypervascularity of the bladder wall, flash echoes within lumen, pronounced urine inflow jet from affected kidney; on spectral analysis diastolic hyperaemia of these vessels. Note  Diagnosis, however, always made by urine analysis. Isolated cystitis not considered a mandatory indication for VUR testing any longer.

15.7.2.10 Traumatic Changes Intravesical clots, haematoma of the bladder wall, bladder rupture. The latter (particularly in conjunction with inconsistent history) suspicious for NAI. US Findings • Clots: more or less spherical formations of intermediate and potentially inhomogeneous echogenicity in the bladder lumen; may be adjacent/fixed to wall by fibrin layers. Can become large and cause (intermittent) obstruction. • Wall haematoma appears as tumour-like thickening with changing echogenicity—depending on age of haematoma. • Rupture: site of rupture sometimes difficult to see, only after filling via catheter. Most common observation—reduced bladder capacity and perivesical fluid (intra- or extraperitoneal). Tip  Filling the bladder with ultrasound contrast agent as done for ce-VUS will help to clarify suspected rupture. This can also be used for US urethrography (while voiding or by catheterisation with retrograde filling or pull-back manoeuvres during saline/UCA instillation).

15.7.2.11 Vesico-Ureteric Reflux See respective entry above.

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15.7.3 Paravesical Changes Sufficiently filled bladder—ideal window to deeper pelvic spaces, for assessment of internal genitalia, rectum/bowel, pouch of Douglas. Typical US Findings Free fluid, may be simple (no echoes—simple ascites) or complex (with echoes, sedimentation, fibrin bands—e.g. after trauma/haemorrhage, in peritonitis/ inflammation). Tip  Digital rectal palpation during real-time US may improve potential to define origin/entity. Potentially fill bladder/rectum by saline infusion.

15.7.3.1 Abscess Formations Typical complication of perforated appendicitis, other bowel inflammatory conditions with perforation, adnexal inflammation; may also arise from urachus remnants—see respective chapters. US commonly shows formation with typical wall, with hypervascularity on CDS, centrally filled of complex fluid, potentially with sedimentation and some included air; sometimes coproliths may be found with in abscess. 15.7.3.2 Tumours of Paravesical Region Most commonly arise from pelvic floor, internal genitalia or prostate (rhabdomyosarcoma, ovarian tumours), sacrum (most commonly sacral teratoma), and neuroblastoma/ganglioneuroblastoma or PNET (which may arise presacrally). No specific US signs—see respective chapters. 15.7.3.3 Cystic Perivesical Structures DDx: ventral meningocele, cysts from internal genitalia (e.g. (para-) ovarian cyst, hydrosalpinx, paravaginal cysts and vaginal atresia, cystic seminal vesicles), mesenteric cyst, cystic venolymphatic vascular malformation, focal ascites collection, abscess, seroma, dublication cysts, etc.

15.7.4 Role of US Ideal for assessing bladder pathology and depicting all paravesical formations: • Often origin may be depicted—use full bladder and meticulous scanning technique with additional perineal access, filling of bladder/rectum, graded compression, etc. • Differentiate solid from cystic structures. Note  In suspected malignancy, additional cross-sectional imaging for initial preoperative assessment, anatomic information, and staging are often necessary.

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15.8 US of Male Genitals US used for external genitalia (scrotum, testis, inguinal canal), seminal vesicles: • Prostate usually only seen in older children—unless in major pathology (e.g. cystic dysplastic seminal vesicles, ectopic ureteral insertion, prostate calcifications after infections, tumour/rhabdomyosarcoma).

15.8.1 US Technique Scrotum/Testis High-resolution linear transducers with highest feasible frequency. Note  Avoid high sound pressure by reducing output gain. Always assess testis in longitudinal and axial sections, compare both sides, following structure towards inguinal canal. Use of stand-off pad can be cumbersome; plenty US gel advised. Tip  Respect privacy of patients even if they are not adults! Volume calculation: ellipsoid equation—depth (cm) × length × width × 0.5 = volume (mL). Dynamic investigation of mobility of the testis, reducibility in case of inguinal position can be assessed; the same for herniated material (reducibility of herniated bowel/mesentery?). Prostate/Seminal Vesicle Commonly curved linear array; (phased) linear transducer preferred if size/bladder filling allows. Apply age-adapted frequencies. Access area through filled bladder or by perineal access. (a) CDS CDS essential for assessing inflammatory conditions and torsion. Spectral analysis comparing both sides mandatory. Vascular supply assessed by following main vessels into inguinal area/canal. Note  Always assess both testes; vessels have to be documented in scrotal wall, testicular capsule, and within parenchyma as well as in epididymis.

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Penile US Rarely necessary in childhood unless for ureteral problems (see chapter urinary tract/bladder and entry PUV). However, haematoma/injury, cysts/diverticula, duplications, postoperative problems can be assessed/visualised. Note  Urethra always best assessable during voiding. Penile US should be complemented by perineal/urinary tract US.

15.8.2 Normal Findings Testis: ellipsoid with homogeneous echogenicity, with spleen-like appearance, some increased echogenicity at hilus. Above testis: cape-like or nodular epididymis, testicular appendices better visible with some hydrocele. Some minor fluid around testis is physiologic. Size in neonates ~2 mL, during childhood increasing with growth, mostly during early puberty when testicular size reaches ~15 mL. Volume calculated by ellipsoid equation as for kidney. Depiction of intratesticular vessels depends on equipment and patient maturity. In neonates intratesticular vessels more difficult to see, whereas during puberty intratesticular vessels must always be visible.

15.8.3 Common Pathologic Findings 15.8.3.1 Hydrocele Defined as some fluid in scrotum around testis and/or in processus vaginalis, common in neonates—not to be confused with normal minor fluid formation (Fig. 15.48). Fluid anechoic, some sedimented echoes may exist particularly in/after chronic conditions. Hydroceles may contain echoes—e.g., after foetal meconium peritonitis often echogenic meconium remnants or calcifications can be detected. Giant hydroceles (even if reactive) may impair testicular perfusion—need to be relieved. • Spectral Doppler may help in assessing asymmetric flow patterns as a sign of perfusion impairment. Note  In older patients secondary to underlying condition (e.g. tumour, torsion, trauma—haematocele, inflammatory process, varicocele). DDx Fluid in scrotum secondary to inguinal hernia/ascites; sonographic key—continuity of fluid through inguinal canal into abdominal space.

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Fig. 15.48  Hydrocele. (a) Axial section—both testes/scrotum: right-sided hydrocele; the minimal fluid on the left side is physiologic in neonates. (b) Longitudinal section: fluid confined to scrotum, no funiculocele. Note small cyst of epididymis (c) Echogenic remnants of meconium (*) after foetal meconium peritonitis floating in hydrocele next to testicle and within inguinal canal (arrow)—dual image

Fig. 15.49  Undescended testis. Testis seen in inguinal canal (a, +  +) or intra-abdominal (b, 1+ …+) lateral to nearly empty, thick-walled urinary bladder

15.8.3.2 Undescended Testes Common finding in early infancy; may be associated with unstable testicular position. Physiological delay of testicular descend may spontaneously mature/resolve. US Findings Testes not located in scrotum: • Carefully assess inguinal canal, region next to the abdominal wall, near internal orifice of the inguinal canal for testicular structures (Fig. 15.49). Non-descended testis may be smaller and dysplastic, prone to malignant conversion.

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Intra-abdominal testicular position (often adjacent to bladder or psoas muscle) more difficult to depict, particularly as undescended testes may be dysplastic and small, exhibit somewhat altered echogenicity—thus definite identification sometimes impossible. May even be found at the lower pole of the spleen or kidney. Note  This also applies for MRI where typical testicular signal may be lost in small dysplastic testes. Increasingly value of US (and imaging in general—impact on treatment?) questioned, as often testicular position estimated higher on US than in reality—due to cremasteric reflex when touched by transducer by pulling testicle up into inguinal canal or abdomen. Role of US • To find position of testes. • Potentially to assess for reducibility/mobility. • Assess size, parenchymal structure, perfusion for depiction of (hypo-)dysplasia. Note  Always perform a basic assessment of the urinary tract, as there may be associated conditions.

15.8.3.3 Varicocele Venous impairment, leading to dilatation and tortuosity of veins of pampiniform plexus, most commonly found in peripubertal boys. Commonly on the left side: • May cause hydrocele, eventually infertility. If in untypical age, on the right side, recurrence after treatment: always assess for potential underlying abdominal tumours causing congestion of testicular draining vein (particularly Wilms’ tumour, adenopathy, retroperitoneal tumours such as neuroblastoma/ganglioneuroma or metastases)—perform abdominal survey. US Findings “Sack of worms”-like appearance of tubular/circular anechoic structures that may change size during Valsalva manoeuvre. Accompanying hydrocele, potentially asymmetric testicular size (Fig. 15.50). CDS Particularly with Valsalva manoeuvre bidirectional/undulating venous flow/retrograde flow direction visualised (Fig. 15.50). Depending on the amount of flow/flow direction, US can grade varicocele (used for follow-up/indication for surgery): • Grade I: clinically normal, slight increase of venous plexus structures during Valsalva.

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Fig. 15.50  Varicocele. (a) “Sack of worms”-like appearance of dilated veins entering into scrotum (inguinal cross section). (b) Vivid colour signals with venous flow profile on Valsalva manoeuvre (similar section as a)

• Grade II: palpable dilatation of externally visible enlarged veins that can be sonographically seen even without Valsalva; change of flow direction during Valsalva. • Grade III: huge dilatation and tortuosity of veins are obvious on clinical inspection (sack of worms), constant inverted flow, even without Valsalva manoeuvres.

15.8.3.4 Cystic Dysplasia of Rete Testis and Seminal Vesicles Cystic dysplasia of rete testis: rare condition, associated with urogenital malformation. Note  Not tubular ectasia as in adults resulting from obstruction but congenital malformation deriving from failure of fusion of afferent ducts. US Findings Multiple, particularly pseudo-confluent cysts/cystic dilatation of rete testis/afferent ducts, associated with parenchymal atrophy/dysplasia. Cysts often located at testicular mediastinum, may compress surrounding parenchyma. Note  Cysts may contain mucoid material causing atypical US appearance—can be mistaken for tumour, abscess, microlithiasis (if with speckled echogenicity), can cause pseudoflow on CDS (if high output power is applied). Cystic dysplasia of seminal vesicles: Rare condition, associated with other urogenital malformations (e.g. ipsilateral MCDK, renal agenesis). US Findings Multicystic, often confluent mass at site of seminal vesicle—usually without echoes, sometimes difficult to differentiate from residual remnant of MCDK in ectopic position (if no kidney seen further up and large).

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15.8.3.5 T  esticular and Paratesticular/Epididymal Cysts/ Spermatocele Rare, present with painless scrotal enlargement. Appears on US like all cysts, usually anechoic mass = uncomplicated cyst. Spermatoceles extremely rare in childhood. Cysts may enlarge, compromise testicular parenchymal growth if large. Differentiation against cystic tumour (teratoma) or ectatic vascular malformation may be difficult. Role of US To depict reason for scrotal enlargement. • Differentiate from rare venolymphatic vascular malformations (have echogenic septations that may also exhibit some flow on CDS, can mimic complex haematocele/hydrocele). • Differentiate against paratesticular cystic masses (e.g. dermoids–often contain some debris/sedimentations, epididymal cysts, spermatoceles (commonly seen only in teenagers), tunical cysts, other causes of enlargement, particularly tumours).

15.8.3.6 Microlithiasis Yet undefined entity with multiple calcifications within testis. Consists of debris with calcific core in seminiferous tubules. Said to be sometimes precancerous (under discussion), associated with infertility: • Some centres recommend follow-up/screening. During course calcification may increase or decrease. Maybe associated with number of conditions (e.g. cryptorchidism, pseudoxanthoma elasticum, cystic fibrosis, chromosomal anomalies, but also after insult to testis). Not to be confused with focal calcification after trauma/infection/surgery, in tumours, or paratesticular calcifications (e.g. after torsion of testicular appendices and meconium peritonitis). US Finding Multiple stippled small calcifications within testis causing blip-like echogenic spots throughout testis (twinkling sign on CDS) (Fig. 15.51). Often bilateral. In future elastography may be helpful for finding early tumourous changes.

15.8.4 Inflammation—Orchitis, Ependymitis Often clinically evident by increased size, reddish skin, pain, with typical laboratory findings. US used to differentiate from torsion or detect abscess/necrosis.

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Fig. 15.51  Microlithiasis. (a) Diffuse microlithiasis. (b) Bicolour mode conspicuously enhances testicular calcifications Fig. 15.52  (Epididymo-)orchitis. Asymmetrically enlarged swollen testis with vivid hypervascularity of testis (and epididymis) on CDS

US/CDS Finding Orchitis: unilateral increase of size of affected scrotum, may be hyperechoic. • Reactive hydrocele, scrotal wall thickening. Secondary abscess/necrosis possible. • Hypervascularisation with hyperemic diastolic flow on spectral analysis (low RI) (Fig. 15.52). Epididymitis: Epididymis enlarged, more or less echogenic, potentially inhomogeneous. Exhibits significant hypervascularisation without hyperperfusion of testis itself. Often associated complex hydrocele: • May also manifest combined with orchitis (epididymo-orchitis). Note  Rarer in children, always think of associated urological problems/ascending infections from prostatic ducts, particularly in urethral obstruction. Paratesticular inflammation may arise from descending infection from peritoneal cavity (peritonitis) or septicemic involvement. Similar findings seen after inguinal surgery with haemorrhage/secondary infection:

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• Typical paediatric entity: echogenic complex material in scrotum around testis— potentially with calcification after meconium peritonitis in newborn. Complications Particularly in orchitis: abscess, necrosis, segmental infarction—can be depicted on US. Note  Differentiation of necrosis versus abscess may be difficult, particularly in early phases.

15.8.5 Scrotal Trauma US used to assess contusion versus haematoma versus rupture. • Contusion: focal inhomogeneous parenchyma seen with swelling of testis, but no parenchymal disruption; continuity of the outer border maintained. • Haematoma: (intra- or extratesticular) easily depicted—CDS allows assessment of viable testicular parenchyma (Fig. 15.53). • Testicular rupture: defined by discontinuity of tunica and intrascrotal haematoma. Viability of different testicular components assessed by CDS, helping to decide on surgery. –– Penis fracture not addressed, as not a query in childhood (sometimes in adolescents)—but well suited for assessment by US (visualisation of haematoma and disruption of tunica).

15.8.6 Torsion Clinically typical acute onset of pain, swelling. Two different types: neonatal extra-/supravaginal torsion; intravaginal torsion common during puberty—usually no impact on therapy except for delayed diagnosis in neonates (often has happened much earlier, e.g. during birth/fetally—then no emergency surgery!).

Fig. 15.53  Scrotal trauma. Testicular trauma with haemorrhage into scrotal sack and injured, partially destroyed testis—obviously with disrupted tunica and irregular contour

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Fig. 15.54  Testicular and hydatid torsion. (a) Enlarged testis with hypoechoic (necrotic) parenchyma—no perfusion on CDS in older testicular torsion. (b, c) Echogenic testicular appendix (b) without flow on CDS (c), consistent with hydatid torsion. (d) Whirlpool sign in testicular torsion— note that CDS visibility of vessels is only granted if there is some residual perfusion

Note  Often adolescent presents delayed because of shyness about seeking care. Thus “missed torsion” with completely necrotic testis not uncommon. US Finding Superiorly positioned, swollen, homogeneously hyperechoic testis—in peracute phase. Some accompanying hydrocele, swelling of scrotal wall (Fig. 15.54). Whirlpool sign/spiral like twisting of spermatic vessels in inguinal canal at entry into scrotum. In longer duration/late torsion echogenicity of testis decreases, may become more inhomogeneous—eventually anechoic when necrotic; secondary abscess formation possible. More complex appearance of associated hydrocele fluid. CDS Asymmetric flow or lack of intratesticular vessels. Twist of vascular pedicle when following it into inguinal canal (“whirl pool” appearance as in volvulus): • Partial torsion may exhibit residual but asymmetric perfusion—firstly affecting veins (haemorrhagic infarction). • After (spontaneous) detorsion, transient hyperaemia may be seen.

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Note  Mandatory to depict intratesticular flow and prove symmetry with spectral Doppler analysis—torsion can only be excluded when symmetric intraparenchymal flow profile in arterial and venous compartment is depictable. In every suspicion of torsion on US, emergent surgical exploration mandatory. US-guided detorsion/manual relief of torsion: detwisting testis by rotation in steps of 180°, checking for reappearance of perfusion—does not obviate surgery as partial detorsion may still exist (reactive hyperaemia will always show some asymmetric perfusion—thus residual partial torsion cannot be ruled out).

15.8.6.1 Torsion of Appendages Quite common. Important DDx for testicular torsion/inflammation (clinical findings may be similar) or inguinal hernia. US Finding Enlarged appendage (hydatid) with lack of perfusion, hyperaemia of adjacent structures, but always symmetric intratesticular perfusion. Often some hydrocele, scrotal swelling, epididymitis-like changes observed (Fig. 15.54b, c). After appendiceal torsion extratesticular calcifications often present. DDx Criteria Scrotal oedema, normal testis, hydrocele, increased vascularisation. No inguinal hernia.

15.8.6.2 Inguinal Hernia If inguinal hernia detected, try to follow through inguinal canal, assess inner ring and describe content (mesentery, fluid, intestines—potentially with peristalsis, perfused bowel wall?) Other rare hernia contents: parts of bladder, in girls ovaries/uterus. Particularly if incarcerated—confusing images seen; sometimes spermatic cord vessels compromised, thus endangering testis. May sometimes only be seen with increased intra-abdominal pressure—consider provocative manoeuvres (imaging while crying/straining, Valsalva, image with patient standing). Note  A “soft”/open inguinal canal physiologic in preterm newborns; movement of mobile testis or entrance of bowel commonly observed—no worry if transient.

15.8.7 Testicular Tumours Rather rare in childhood, most commonly germ cell tumours or teratoma.

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Fig. 15.55  Testicular tumours and DDx: (a) Small tumour (+ …+) slightly resembling a cystic dysplasia of the rete testis. (b) Larger testicular tumour x … x), nicely outlined by hypervascularisation on CDS (c). (d) Testicular teratoma with a solid component (…) on CDS. (e) Huge haemorrhagic spermatocele only entirely imageable by a curved array

US Findings Typically appearance of ovoid space occupying lesion. May be cystic, particularly in teratoma/epidermoids, or completely solid. May have more complex cystic appearance with septae (Fig.15.55) • Often mild associated hydrocele. Definition of underlying entity rarely achievable. • Always assess pelvic/retroperitoneal lymph nodes, and perform abdominal survey. Secondary involvement in systemic diseases (e.g. leukaemia/lymphoma, neuroblastoma) where testis can even serve as host region for recurrence, involvement may be uni- or bilateral. DDx Intratesticular cysts, dermoids, septated hydroceles, epithelial cysts, cystic dysplasia of rete testis, intratesticular ectopic adrenal tissue, infection/abscesses/necrosis, posttraumatic alteration. Note  Rhabdomyosarcoma in male pelvis mostly from pelvic floor muscles, prostate, seminal vesicles, or bladder, rarer in scrotum.

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No other sonographically important aspects of prostate need to be addressed in childhood; only sometimes after infection prostate calcification may be seen, as well as an atypical appearance of enlarged seminal vesicles in cystic dysplasia and then often combined with other urogenital malformations.

15.8.8 Role of US and Additional Imaging US—ideal initial imaging tool with high reliability, when performed skillfully. Supplementing Investigations • Scintigraphy and MRI have been performed for torsion—but potential time delay usually demands early surgery in unclear cases. • In tumours: staging by CT/MR. • Assessment of ectopic testis/cryptorchidism: may benefit from MRI, although small dysplastic testis in abdominal cavity may be difficult to depict—many centres perform laparoscopy if testis not found in pelvis/inguinal region directly. • Assessment of complex genital (cloacal)/intersex states: may benefit from MRI/ ce-CT and fluoroscopy/genitography. • Angiography of spermatic vein only performed in complex/recurrent varicocele for therapeutic reasons (embolisation in the same session).

15.9 Female Genitals 15.9.1 Indications Suspected genital malformation/disease by clinical findings on inspection, ambiguous gender, associated urogenital malformation, hormonal abnormality (e.g. precocious puberty, adrenogenital syndrome).

15.9.2 Requisites Sufficiently filled bladder mandatory for detailed assessment. Perineal approach very helpful—looking at vagina/pelvic floor/rectum (cloacal malformation): • In unclear findings/obvious pathology, filling of the bladder and vagina with saline helpful (“Sonogenitography”) (see respective chapter). • For depiction of fistulae, optional/additional UCA instillation.

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15.9.3 Transducers Particularly in neonates, high-resolution linear/micro-curved arrays applied. Otherwise use curved linear areas with highest applicable frequency. Transvaginal investigations usually only performed after puberty: • Some centres perform transrectal investigations.

15.9.4 How to Perform Investigation Consecutive longitudinal and axial sections through region of genital organs behind bladder by rotating transducer into respective organ axis of fallopian tube, ovaries, uterus. Take size measurements, document findings: • Always include entire US of all other pelvic structures/urinary tract, include adrenal glands. Measurements particularly important in suspected hypodysplasia or early onset of puberty: • Compare results to tables with normal values. Always try to assess detailed structure of ovary (size? follicles present?) and uterus (size, shape, horns, wall structure/endometrium?): • In older girls additional assessment of breast valuable for complete work-up in hormonal imbalance.

15.9.5 Normal Findings Uterus  Changes during growth/development (Fig. 15.56): • In neonate (stimulated by maternal hormones): rather large, with long cervix, endometrium nicely differentiated. • In infancy/early childhood: small, difficult to assess. • With onset of peri-/prepuberty/hormonal activity: uterus grows again. Eventually becomes shape of typical adult uterus—pear shaped  =  relatively short cervix, large body, exhibits well-differential wall/endometrium (varies throughout cycle). Uterus muscle rather hypoechoic, with clear contour. Thickness of endometrium depends on hormonal situation. Often positioned not strictly sagittal/in midline— some deviation physiological:

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Fig. 15.56  Different stages of uterine development. (a–c) Longitudinal section: (a) neonatal shape, (b) infantile appearance, (c) prepubertal configuration. (d, e) Axial section: (d) pubertal uterus with prominent ovarian follicles, (e) adult uterus with prominent endometrium

• Useful measurement for assessing maturity: index made from corpus to cervix length. Cervix longer in neonates, corpus longer in mature girls. Vagina  Tubular muscular structure with central lumen, reaching from cervix to external orifice/vulva • For assessing patency/duplications, filling of vagina with saline infusion necessary. • Distal portion only visible by perineal US, once symphysis ossified. This approach also useful for distal vaginal atresia—imperforated hymen. Adnexae  Fallopian tube/adnexa often poorly visualised unless ascites or hydrosalpinx. Ovaries  Undergo stepwise development, being relatively prominent in neonate (maternal hormones) with multiple follicles that create cyst-like appearance: • Remember: ovary  =  “cystic organ”; ovarian “cysts” usually represent normal follicles. • In neonates ovaries positioned throughout abdominal cavity, sometimes at unsuspected high location, may have large cysts (Fig. 15.57).

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Fig. 15.57  Normal neonatal “cystic” ovary. (a) Typical large “multicystic” neonatal ovary (1  +  …+) that may be positioned relatively high and ventrally. (b) Ovary during childhood— smaller, more difficult to find (full bladder mandatory), in this case exhibiting physiologic follicles that may not be depictable in many cases. (c) Pubertal/adult ovaries with multiple follicles (physiologically a “multicystic organ”), observe large paravaginal/retro-uterine cyst and some ascites. (d) Ovarian “functional” cyst (not always able to be differentiated from a cystic teratoma on a single US exam)

• In infancy/childhood during “silent” phase—ovaries small, often difficult to depict. • With onset of hormonal activity/(pre−/peri-) puberty—ovaries grow, manifest as typical “multicystic” retrovesical organs lateral to uterus—more peripheral follicles, some central tissue. Follicles vary in size, neonatally far more than 1 cm, in infants usually less than 5  mm, in puberty—depending on phase of cycle—up to 4 cm.

15.9.5.1 Sonogenitography Assessment of internal genitalia after vaginal filling via small flexible catheter with saline infusion (for further details see respective chapter): • Bladder also needs to be full/filled. • Sometimes simultaneous rectal saline enema may be helpful (prove absence of uterus/vagina, depict fistulae). Tip  Rinse catheter before inserting to avoid introducing obscuring air into vagina.

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15.9.6 Pathologic Findings 15.9.6.1 Congenital Malformations Vaginal Septum and Duplications Midline anomalies—most commonly only recognised if outflow occluded: cystic formation manifests. Alternatively filling by saline infusion after careful catheterisation may support diagnosis, additionally may help detect potential connections, particularly when supported by ce-US and perineal US: • Echogenic septum dividing vagina will become visible. • Echogenic ultrasound contrast agents (UCA) may pass from one to another cavity through potential opening. Vaginal Atresia Atretic (single/duplex) vagina—usually thick membrane, leads to hydro−/ haematocolpos: • To be differentiated from hymenal atresia by thickness of septum (hymen—thin membrane). US Findings Difficult to evaluate without filling of obstructed vagina. Obstruction manifests as more or less prominent tubular-ovoid space occupying lesion in midline below bladder in anatomic area of the vagina (Fig. 15.58): • Sonomorphologic aspect depends on content (fluid, haemorrhage, sedimentation, etc.). • Can become huge, may also include cervix/uterus—then uterus seen by meticulous assessment as (often small) pear-shaped end of “cyst,” connecting fluid-­ filled cavity to salpinx (hydrosalpinx) (Fig. 15.58). • Secondary ascites. Associated with uterine duplication if duplex vagina. Vaginal Fistula Remnant of disturbed foetal development. Often associated with urogenital/cloacal malformations: • Also after trauma, infection, surgery. Commonly connect to distal urethra (urogenital sinus) or (additionally) rectum (cloacal malformation): • This combination only seen in phenotypic female babies. Fistula to more proximal parts of the vagina/bladder usually have acquired origin:

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Fig. 15.58  Vaginal atresia. (a–c) School-age girl with “pelvic tumour”: inhomogeneously echogenic cystic-tubular mass that may exhibit sedimentations (b, sagittal view) in anatomic location of vagina; small residual uterus sitting on top (c, …+,). (d) Perineal US exhibits thick distal occlusion of the vagina in vaginal atresia. (e) US genitography with UCA: vaginal duplication in a child with uterine duplication, hemivaginas not connected; the noncontrast-filled (anechoic) vagina is atretic

• Ectopic ureteral insertion into the vagina (even via ureterocele) possible—often associated with renal dysplasia/obstruction. US Findings Indirect signs: fluid-filled vagina, potentially change in filling/size before or after voiding/with variable bladder filling: • Fistula tract more easily visualised after filling of bladder/vagina (sonogenitography)—US contrast agent very helpful in this query. • Fistula to rectum may be visible by gas bubbles coursing through rectal wall into vagina. • Perineal US most helpful for these queries. Tip  For finding these pathologies well-filled bladder and fluid filled rectum helpful—consider filling by saline using a catheter/rectal tube to grant sufficient access and discrimination of structures. Other Vaginal Malformations Cystic changes rare. May be remnants from Müllerian/Wallerian duct or secondary to hypoplastic vagina: • Cysts in vaginal wall (e.g. Bartholin cysts). • Other paravaginal cysts may also manifest secondarily (infection, after surgery, etc.).

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DDx Para-urethral cyst, urethral diverticula, ectopic ureterocele, cystic teratoma (rare). US Finding • Typical visualisation of more or less complex cyst. • No further specific imaging features. Vaginal Aplasia Rare. Potentially combined with aplasia of uterus. Only clearly outlined after filling of the bladder/urethra (during voiding) and rectum and supplementing perineal US. • Vaginal remnants in phenotypical boys also occur—may be missed if no assessment before AND during/after voiding. VCUG/fluoroscopic genitography may be helpful. Uterine Malformations Number of uterine malformations: aplasia/hypoplasia, unicornuate/bicornuate/ duplex (didelphis)/arcuate/(sub-)septated uterus, cervical atresia. Usually seen either neonatally or at the beginning of puberty, hardly detectable during infancy/early childhood due to physiologic smallness without hormonal stimulation. US may depict abnormalities, particularly if more severe—actively search for, more easily seen on transverse sections (Fig. 15.59), best on (reconstructed) coronal views using 3DUS as known from adults (see respective chapter). • Exact classification often needs 3DUS and/or sonographic colpography after instillation of saline (the latter not performed in childhood). a

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Fig. 15.59  Uterine duplication. (a, b) Uterine duplication—more difficult to see during hormonally inactive infancy (a, + …+) than in neonates/during puberty (hormonal stimulation enlarges uterus and causes endometrial prominence) (b)

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Note  If uterine malformation depicted/suspected: always assess entire urinary tract—as well as vice versa (e.g. in urinary tract malformations, always meticulously assess genitalia). Ovarian Malformations Agenesis/dysgenesis may occur with various syndromes/hormonal conditions, particularly in intersex queries. Note  Hypo-/dysplastic ovaries very difficult to visualise, even with MRI, as they lack typical shape/size/(echo-)structure (e.g. do not contain follicles/cysts). Can be found in quite unusual locations (e.g. labia, inguinal canal, far latero-cranial in pelvis, even in abdomen/ventrally). • Multicystic ovary: usually manifest later—exhibit multiple large follicles in significantly enlarged ovary. • Polycystic Ovary Syndrome: metabolic disease that affects ovaries (oligo−/ amenorrhoea, hirsutism, acne, obesity, diabetes, insulin resistance, high prolactin or androgen levels = hormonal imbalance,…); disease of adulthood/adolescents—diagnosis not based only on US findings. However, often large ovaries with numerous peripheral, rather small follicular cysts seen, with broad echogenic central stroma (Fig. 15.60a). Definition (in adolescent and adult females— “Rotterdam criteria”): –– Ovarian volume >10 cm3/ovarian area 5.5 cm2. –– >12 follicles per ovary, 60°, cartilaginous angle (β) half of femoral head. • Potentially delayed ossification. Subtypes: • • • •

II a +: physiologic immaturity. II a–: maturation deficit during first 3 months. II b: after third month of life, α≤60°. II c: developmentally dysplastic hip—definitely endangered, needs treatment: –– Dynamic stress manoeuvres are mandatory. • D (IId)—usually unstable hip with beginning decentring: –– Dynamic stress manoeuvres mandatory. –– Very rounded bony rim. –– Initially displaced cartilaginous acetabulum. –– α = 43°–49°, β > 77°. –– Only treatment option = fixation. Decentred Hip: Type III (Fig. 16.6) US Criteria Femoral head has pushed cartilaginous acetabular roof cranially: • • • •

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Fig. 16.6  Pathological hips (Graf classification). (a) Immature hip, slightly rounded roof (>3 months of age—type IIa). (b) Endangered hip: severely rounded bony roof, displaced cartilaginous roof, dynamic assessment mandatory (type D). (c) Dysplastic—decentred hip with flat bony roof—type III. (d) Luxated hip—by definition cartilaginous labrum compressed between femoral head and iliac bone (type IV)

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• Type III B—cartilaginous acetabulum small, compressed, distorted + structural anomalies + some echoes and inhomogeneous. Only in untreated and chronically dislocated hips − sign of severe damage (remark: very uncommon in Middle Europe). • Therapy: needs repositioning and fixation. Luxated Hip: Type IV (Fig. 16.6). US criteria: • • • •

Femoral head displaced from joint space: Luxated in cranial, lateral or dorsal position. Cartilaginous acetabulum herniated and displaced caudally: Pressed in between femoral head and iliac bone—increased inhomogeneous echoes. • Sometimes difficult to find bony rim—reliable measurements often impossible/ not required. • Dynamic assessment helps to evaluate for repositionability. Note: wrong angulation will cause wrong results—dedicated instruments are available to reduce probability of this common pitfall (Fig. 16.7) Results in Rosendahl Modification According to morphology (using Graf angle discrimination): • Immature, mildly dysplastic, severely dysplastic. Using stability: stable, dislocatable, dislocated. DDH According to Harcke • Classification: normal, lax with stress, subluxed or dislocated (see Fig. 16.3b). Note  Method more subjective; also includes description of hip stability. Neither accuracy nor population-based rates of pathological hips based on this technique have been published. Hip Assessment Based on Femoral Head Coverage • All outside accepted limits = DDH—less potential for grading, used as initial screening tools to assess for normal or abnormal hips. • In abnormal hips, either Harcke or Graf method can be applied additionally for treatment decisions.

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Fig. 16.7  Common pitfall in Hips US = wrong angulation with respective implication on angle measurements in the Graf and modified Rosendahl method: As demonstrated in schematic drawing of a table corner, the angle will appear different depending on the viewing angle and perspective (a), influencing angle measurements on US (b) – where the correct angle measurement is only lower Hip US image, whereas the upper image exhibits wrong angle measurements; the malposition is recognisable by missing femoral structures on the US image. Note that the measurement lines do not have to cross in one point to be correct! (c) Shows a technical device (arrow) that may help to avoid accidental tilting of transducer

16.6 Other Conditions of Hip Joint 16.6.1 Arthritis and Inflammation of Hip Joint As in all joints, examination of contralateral (not affected side) helpful for comparison (TIP: start there—less painful, know individual normal anatomy). Most common cause: transient synovitis of hip. US findings and Staging • Joint effusion, thickening of joint capsule (Fig. 16.5b). Note  Differentiation (viral, bacterial, septic, rheumatoid) impossible by US. Usually achieved by clinical data (possibly US-guided arthrocentesis).

16.6.1.1 Capsular Thickening Can be measured, does not need to be present, no cut-off value, can have varying echogenicity: • Appearance not specific—depends on kind of inflammation, age, duration, transducer used. • Sometimes CDS shows hypervascularisation of capsule (Fig. 16.5c). • If increased vascularity depicted: spectral analysis may show diastolic hyperemia: • Unless increased joint pressure, then diastolic perfusion impaired.

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16.6.1.2 Joint Fluid/Effusion Widening of joint space due to fluid, forces capsule to convex shape: • Simple/uncomplicated: clear fluid, up to 10  mm (intraindividual difference >3 mm) (Fig. 16.5b). • Complicated: larger, echogenic particles within, potentially significantly thickened synovial layer; may reflect also haematoma / haemarthros (e.g. haemophilia) • Suspect septic/bacterial arthritis (Fig. 16.5c). Note  In osteoarthritis of infants, there may be distention and consecutive luxation and osseous defects. Luxation can be identified by applying DDH US techniques (e.g. Graf’s criteria)—search for it! And  Simple effusion does not rule out bacterial / septic arthritis, and complicated effusion does not proof septic arthritis = if any doubt do (US-guided) sampling.

16.6.2 Hip Osteoarthritis US findings similar to any other joint. Usually unilateral, whereas transient synovitis may occur on both sides, as well as Perthes disease (rarer). Particularly after long-standing and bacterial arthritis, defects may remain—with poor ossification of femoral neck and defects in convexity of femoral head. Important to assess and monitor development of disease—persisting effusion always hints towards underlying condition or Perthes, where osseous defects can also/additionally be seen.

16.6.3 (Femoral Head) Epiphysiolysis/Slipped (Capital Femoral) Epiphysis US superior to plain film in infants due to poor ossification of femoral head— improved assessment, same approach accounts for all other joints with cartilaginous epiphysis (e.g. shoulder, elbow—birth trauma) (Fig. 16.8): • Displacement in any direction—US access from different directions and positions recommended. US Findings Typically anechoic cartilage of femoral head with or without ossification centre slipped: • Continuity of bone margin disrupted at level of physis—step-off phenomenon. • One millimetre displacement equals approximately 5° displacement on plain film.

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Fig. 16.8  Epiphysiolysis in a newborn after birth trauma. Note discontinuity between ossified bone and hypoechoic cartilaginous epiphysis indicating dislocation of epiphysis

Complex joint fluid representing haemorrhagic components—particularly in acute phase. Periosteal reaction—late stage. Secondary changes of surrounding soft tissues. US-guided reposition feasible. Note  If tolerated, dynamic assessment may reveal pathologic motion at physis. Same criteria apply to epiphysiolysis of any other joint in neonates and infants.

16.6.4 Perthes Disease Definition Avascular necrosis of femoral head of unclear aetiology and unknown origin, 20% of affected children have history of transient synovitis of hip. US Findings and Staging Grade I: • Potentially only joint effusion. • Slight asymmetric reduction in height of epiphysis as well as femoral head on affected side. • Contour of femoral head is maintained. Grade II (Fig. 16.9): • Fragmentation; irregular disruption of outer contour of bony femoral head— sonographically irregular. • There may be secondary effusion.

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Fig. 16.9  Perthes disease. (a) Scattered epiphysis of femoral head in early Perthes disease (stage II). (b) Both hips imaged for comparison (split image technique): note reduced height of affected right (R) femoral head (Grade IV—US appearance varies with stage); additional imaging compulsory (plain film+MRI)

Grade III and IV: • • • •

Reparative mechanisms—femoral head increasingly homogeneous. Significantly reduced femoral head height. Joint effusion diminishing. However, lateralisation and atypical contour of remodeled femoral head persists.

Note  In suspicion of Perthes always perform plain films and (dynamic contrast-­ enhanced) MRI

Musculoskeletal and Other Small Part US in Childhood

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17.1 Investigation of Bones, Joints, Tendons 17.1.1 Requisites and Technique Transducers and Techniques • Linear transducers with high resolution (18/12–5 MHz). Features such as trapezoid mode, image compounding and harmonic imaging helpful. • In very superficial structures stand-off pad helpful, however, using high-­ resolution transducers stand off-pads not routinely needed, particularly if US gel used liberally. • For deeper structures, curved linear arrays and lower frequencies helpful—as trapezoid mode of linear transducers usually lacks same penetration (or try to get out of trapezoid mode). • For long structures such as tendons, extended view techniques helpful, alternatively split/dual image technique. • In tumours or inflammatory conditions (abscess, arthritis, etc.): (a) CDS (and potentially ce-US) helpful. M. Riccabona (*) Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] G. Schweintzger Abteilung fur Kinder und Jugendliche Neonatologische und padiatrische Intensivstation, LKH Leoben/Eisenerz, Leoben, Austria e-mail: [email protected] B. Coley Department of Radiology, ML5031, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA e-mail: [email protected] © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_17

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• Elastography—promising future method for assessment of tendons and tumours, but not yet validated in children. Positioning and Handling • Varies depending on affected area, therefore no standard planes. • Important to choose comfortable position that minimises pain. • Start investigation at non-painful area, work to area of disease—in young children consider applying analgesic ointment before investigation. Tip  Very often initial evaluation of contralateral normal side proves valuable— serves as intraindividual normal reference, helps optimise equipment settings and enables child to get used to scanning (reducing anxiousness and fear). • All joints and pathologies usually assessed in two orthogonal sections. • Surface alterations better visualised and documented by 3DUS using surface rendering. Indications Applicable to acute and chronic conditions: • Joint pain or effusions (most commonly used in large joints but also feasible in small joints). • Skin, soft tissue, muscular and tendon disease (e.g., achilles tendon, shoulder capsule, wrist and foot tendons). • Evaluation of unclear swelling, e.g., suspected haematoma or node or cyst versus other causes for bumps. • Suspected tumorous conditions with lumps. • Search for and detection of foreign bodies. • Assessment of all accessible osseous structures (e.g., continuity or focal disruption, callus). • Evaluation of periosteal reaction—exquisitely visualised by US, particularly periosteal thickening and abscess. • Assessment of all accessible peripheral muscles (e.g., follow structures from origin to insertion, show transition zone to tendon or bone). Advantage: US allows comprehensive assessment of all surrounding structures (bones, joints, etc.) and perfusion (CDS). Disadvantage: If very painful or if diagnostic benefit restricted in some areas— US not justify; imaging then performed by plain film, CT or MRI. Restrictions: Deeper joint spaces and bony structures beyond surface not visualised by US—commonly need MRI. Note  In osseous structures, usually only surface component (cortex) assessable for continuity or disruption, e.g., fracture or tumour. If US can penetrate cortical layer (e.g., due to disruption or reduced ossification/calcification by tumour infiltration, osteomy-

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elitis and decalcifying disease), visualisation of processes in deeper bone compartments achievable. Detailed demonstration of all major joints and their US appearance beyond scope here—refer to extended literature and textbooks. Different for non-ossified parts of skeleton in younger age: US ideal for showing cartilaginous structures = primary imaging approach. US shows continuity of cartilaginous parts with ossified bone and/ or other surrounding structures—particularly useful for assessing children with nonaccidental injuries (corner fractures, etc.) or even in diagnosing epiphysiolysis.

17.1.2 Typical Normal Findings Bone If US beam perpendicular, and cortical layer of normally ossified bone intact: only surface echo seen as an echogenic border with complete shadowing behind. Subtle layer seen in front represents periosteum. Note  Pseudo-periosteal layer may occur if gain too high producing strong reflections. Cartilaginous Structures • Hyaline cartilage: usually anechoic/hypoechoic with more or less echoes within, depending on maturity (and setting of US system) (Fig. 17.1a). • Collagenous (fibro-)cartilage: US appearance becomes more echogenic in areas of more fibrous components (e.g., fibrous annulus of vertebral disc, acetabular labrum of newborn and infant hip). • Ossification centres become centrally echogenic, with increasing shadowing (Fig. 17.1b). Remark: Cartilaginous echostructure and contour usually show slight irregularity at transition zone to ossified bone (may represent physis). However, even with this short disruption, surface usually remains continuous.

Fig. 17.1  Cartilaginous epiphysis in infants. Hypoechoic cartilaginous epiphysis with some stippled physiologic echoes representing the venous sinusoids—without (a) and with (b) central echogenic ossification centres causing shadowing

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Joint Capsule and Tendons Depending on angle of insonation, these structures change echogenicity and appearance (anisotropy) (see Fig in respective chapter and Fig). Capsules usually have just one visible layer except for insertion (varies with transducer frequency and resolution). Tendons have several parallel echogenic layers.

17.1.3 Pathologic Findings 17.1.3.1 Fracture • Interruption of cortical contour (high sensitivity). • Additional findings: periosteal reaction, haematoma, later callus formation can be seen, depending on phase/age of fracture (Fig. 17.2): • If dual/split image/extended view techniques or 3DUS used: angle measurements can be performed to define deviation of displaced fracture, provided longitudinal axis of respective bone clearly identified. • In all fractures: periosteal reaction, calcification and callus formation seen as (pseudo-)tumorous, more or less ossified, formation at site of fracture. • In reparative phases: CDS can show hypervascularity and hyperaemia as sign of reparative processes; difficult to distinguish from tumorous or inflammatory conditions.

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Fig. 17.2  Subperiosteal haematoma. (a) Typical early image appearance of traumatic haematoma due to fracture with dislocation. (b) DDx: osteomyelitis versus subperiosteal abscess: may appear similar on US as subperiosteal haematoma in this forearm fracture (c, markers)—not always hypoechoic as in the shown skull fracture, (d) depending on age, etc.

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• Growing fractures and pseudo-arthrosis can be visualised—particularly when performing dynamic study showing not only disruption and distraction of fracture ends but also painless mobility towards each other. Note  US cannot always replace plain radiographs. Plain film simpler and allows clearer definition of dislocation angles, also avoiding possible pain during examination. US demonstration and documentation of entire bone may be cumbersome. But specific applications exist where US is very helpful due to restrictions of plain film: e.g., skull fractures (where plain film is usually not indicated any longer except for nonaccidental injury queries), corner fractures and toddler’s fractures, non-dislocated and ungapping fractures and recently even proposed for assessing forearm fractures (WRIST safe protocol; Ackermann O. Eckert K “Fraktursonografie”, Elsevier, 2019)—but particularly for the latter the bones must be assessed from all directions! (Fig. 17.3) Note  Fractures and dislocation of cartilaginous bone = US domain—much better than plain film, US also used for image-(US-)-guided reduction, e.g., after epiphysiolysis (see Fig. 16.8 in hip US chapter).

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Fig. 17.3  US in fractures. (a) Fracture without destruction of periosteum and slight bending. (b) Subtle skull fracture poorly depictable by plain film; note regional haematoma; (c–f) US of different forearm fractures, also demonstrating possibility of angle (e) and dislocation (f) measurements. (g) Impressive callus formation after femur fracture)

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Remark: In long bones, usually only the part of a fracture close to transducers can be visualised and assessed, as US cannot penetrate healthy ossified bone. If one needs to see entire circumference, scan from every direction. Therapeutic insonation can increase callus formation and bone healing (by causing hyperaemia)—requires specialised equipment.

17.1.3.2 Joint Effusion US highly sensitive in detection. Extremely helpful also in management of rheumatologic and haemostatic disorders. Simple Effusion Sonographically defined by usually anechoic fluid (uncomplicated effusion) within joint space, causing widening of joint and enlargement of joint space. Commonly capsule appears normal, may be slightly thickened (see Fig. 17.5). Complicated Effusion Echoes within fluid, potentially sedimentation (see Figs. 17.4 and 17.5).

Fig. 17.4  Joint effusion with septations (knee arthritis). Relatively clear fluid, some thickening of joint capsule in rheumatoid arthritis, some nodular components indicating pannus formation in longitudinal (a) and axial (b) sections

Fig. 17.5  Thickened joint capsule (a) and hyperaemia on CDS (b). (a) Septic knee arthritis—with marked thickening of capsule and complex fluid. (b) Thickened elbow joint capsule with effusion (osteoarthritis). (c) CDS depicts hypervascularisation (same joint as b)

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Note  US not specific to aetiology or content of effusion (haemorrhagic, proteinous, infectious, etc.). Diagnosis of underlying disease only in combination with clinical context (trauma, inflammation, aseptic necrosis) and laboratory evaluation. Only those parts of joint assessable where US can access. Therefore—to properly assess joint for potential effusion—scan all around joint accessing joint space from different directions not to miss focal effusion in specific compartment, recess or bursa. • US used for guided diagnostic arthrocentesis and drainage (see chapter on interventional US).

17.1.3.3 Arthritis Effusion commonly seen; small amounts detectable by careful examination (see also Sect. 17.1.3.2. Joint Effusion). Typical US feature (high sensitivity, low specificity): thickening of joint capsule with more or less hyperaemia on CDS (Fig. 17.5a). Note  Etiological correlation by US not possible (needs history, physical exam, laboratory findings, etc.). • In rheumatoid conditions capsular thickening can become irregular and nodular, with varying amount of hypervascularisation—US used to guide therapy and assess therapeutic response, also for drug instillation (see chapter on interventional US).

17.1.3.4 Trauma Most commonly, US used to assess disruption of tendons, muscles, bony structures (see above) and apophyseal avulsions in adolescents (Fig. 17.6). Note  In these conditions, do not only assess tendon or joint but also surrounding structures and muscles which may show haematoma or disruption (see respective chapter) (Fig. 17.2a, b). Haematoma • More or less ovoid-shaped mass, with varying echogenicity (Fig. 17.2a, b). • Appearance varies with age, site and kind of haematoma (diffuse bleed into preserved structures, haematoma without preserved structures) and insonation angle. • Old haematoma either resorbs completely, leaves some fibrous scarred tissue or forms seroma (more or less complicated fluid collection with some capsule-like wall), may calcify or even ossify (myositis ossificans), then show complete or punctuated internal echogenicities with posterior shadowing (see below). Rupture of Tendon Extremely rare in paediatric population; dynamic investigation very helpful for ligamentous queries and function assessment, as well as defining compartment and origin/connections.

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Fig. 17.6  US in musculoskeletal trauma. (a) Most important in US of musculoskeletal trauma— observe anisotropy effect; tendens (as well as muscles) appear different depending on the insonation angle: Longitudinal image of a forearm flexor tendon—(a) shows echogenic fibrillar architecture. Transverse image performed at 90°(b) shows bright echogenic reflectors from the tendon (arrow). (c) Transverse image performed off-perpendicular shows the same tendon to now appearing hypoechoic (arrow). (d–f) Apophyseal avulsion on right side (left part of image)—comparison to contralateral normal left anterior inferior iliac spine using split image technique: (d) cross section, (e) longitudinal scan in a different patient with same pathology. (f) Partial rupture of achilles tendon: tendon swollen, hypoechoic, disruption of continuity clearly depictable

Complete tear: continuity of tendon disrupted, often significant distance between lower and upper part (measure distance for treatment decisions)—ends difficult to find and assess. Partial tear: persisting continuity of some parts of tendon, though potentially swollen and altered, whereas other parts are disrupted with some sort of haematoma formation (Fig. 17.6c). Chronic tear/chronic microtrauma—different image appearance: organisation and reparative processes  =  inhomogeneous small spots with some calcifications appear in somewhat unusually and inhomogeneously structured tendon. Tendon may be thickened and edematous—altered echotexture. If tendon sheath intact, there may be thickening and effusion due to chronic alteration with variable hyperaemia and hypervascularisation (CDS). • Elastography promises to become a useful tool for detecting areas of chronic damage. Note  Observe anisotropy effects and potential risk of misreading.

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Fig. 17.7  Baker cyst and DDx of soft tissue cysts. (a, b) Baker cyst (+ +2) longitudinal (b) and cross section (a), the latter showing the connection to joint space (+ +1). (c) DDx in complex cystic masses: “cystic lymphangioma”—cystic lymphatic/vascular malformation. (d) Abscess formation in breast with reactive changes in surrounding soft tissue

17.1.3.5 Cysts Number of situations with soft tissue cysts—potentially connected with joints space—e.g.: • Posttraumatic and chronic stress, seroma remnants; effusion-filled recesses and bursae. • Physiological variations/fluid-filled recesses. • Cystic tumours. • DDx: even in uncomplicated cysts—evaluate if connected to joint space (e.g., Baker cyst), tendon sheath (e.g., ganglion), muscle (e.g., posttraumatic seroma) or vessel (ectasia or aneurysm) (Fig. 17.7). Note  An irregular, thickened and hypervascular wall or complicated echoic content (with potential sedimentations) usually indicates complications—such as inflammation or tumorous origin.

17.1.3.6 Inflammation US extremely helpful for differentiating superficial versus deep soft tissue infection (e.g., fasciitis). Used for depiction of necrosis or abscess and differentiation of other causes. Note  Increases index of suspicion in early phase of osteomyelitis (see below).

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Cellulitis Usually diagnosis made clinically; US used to assess extent of involvement, complications (abscess) and differentiate from fasciitis: • US findings: enlarged echogenic subcutaneous tissue with irregular ovoid fluid collections; reticular hypoechoic striations occur (but US findings nonspecific— insect bites, etc. may appear similar). • CDS: hypervascularity and hyperaemia. Fasciitis Often induced by minor superficial skin lesion and in immunocompromised patients: • US findings: perifascial fluid, swollen and echogenic subcutaneous layer (phlegmonous), poor fascial border, muscle usually spared (Fig. 17.8). In necrotising fasciitis, air/gas seen—no further US access to deeper structures achievable (as in subcutaneous emphysema—see Fig. 17.22). Tendinitis: Tendovaginitis/Synovitis Not so common in children, however increasingly observed with excessive sports and training with non-physiological strain (“overuse injury”): • Characterised by swelling and thickening of tendon sheath with some effusion, tendon inhomogeneous and thickened, surrounding soft tissues can be edematous and swollen (Figs. 17.8 and 17.9). • CDS: often hypervascularity and hyperaemia. a

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Fig. 17.8  Subcutaneous tissue pathology. (a) Oedematous subcutis and thickened, multilayered fascia that is accompanied by some fluid. (b) Phlegmonous fasciitis with huge swelling and fluid-­ filled septae Fig. 17.9  Tenosynovitis. Echogenic swollen tendon with fluid within the tendon sheath; note echogenic adjacent soft tissue as a sign for oedematous-inflammatory reaction. Plenty of US gel used causing the superficial dark area in front of the skin with some echoic spots

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Osteomyelitis Specific pathophysiology in early childhood: predominantly starting at physis involving also joint as septic arthritis always affecting growing plate. US very helpful in early phase. • US findings (Fig. 17.10). –– Thickening of joint capsule. –– Periosteal thickening. –– Subperiosteal collections—subperiosteal abscess, DDx haematoma (Fig. 17.10, see also Fig. 17.2c). –– Osseous surface disruption (when extending into spongiosa in later phase), increased sound penetration into bone when already demineralised. –– Adjacent inflammatory reaction and soft tissue oedema, (secondary) soft tissue/periosteal abscesses. –– CDS: hypervascularisation and hyperaemia. Note  US  =  first-line exam, MRI mandatory for early detection, complementary plain film shows soft tissue swelling and only in later stage osseous changes.

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Fig. 17.10  Abscess and osteomyelitis. (a) Subcutaneous abscess after injection. (b) 3DUS of a parosteal abscess after IV line-induced thrombophlebitis in a newborn. (c) Subperiosteal abscess (axial section) with more complex appearance and enormous surrounding inflammatory changes. (d) Subperiosteal abscess—longitudinal view (+ +). (e) Osteomyelitis (split/dual image technique): normal knee of an infant on left image. The image of left knee (L) shows the abscess formation with a more prominent sound penetration into the less ossified distal femoral metaphysis. Note irregularities of the cortical border close to the physis

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17.1.3.7 Neoplasia Bone tumours: US findings in all bone tumours with extraosseous components or bone erosion are very sensitive but nonspecific. Childhood-specific bone tumours: osteosarcoma and Ewing sarcoma: • Added value to mandatory plain film: assessment of soft tissue components, periosteum, vascularisation. Other soft tissue tumours: US findings nonspecific, show tumour and relation to surrounding structures (osseous, joint and vascular), give information on components (solid, cystic, necrotic, vascular, etc.). • Common benign childhood entities: Lipo(-fibro-)ma, haemangioma, neurofibroma, lymphatic malformation, vascular malformations, fibromatosis of sternocleidomastoid muscle (neonates—see neck chapter). • Malignant tumours: Practically only rhabdomyosarcoma, rare other sarcomatous tumours exist. • Cutaneous metastasis: except for neuroblastoma extremely rare. US Appearance All features known from other imaging modalities (Fig. 17.11): • Codman triangle and spicules—echogenic disruption of more or less homogeneously anechoic tumour bursting from cartilaginous or bony surface. • Periosteal infiltration. • Infiltration of soft tissues. Also assess: • Relation to joint, physis or muscles, tendons and vessels. • Depict solid or cystic component of soft tissue tumours. • Use CDS to demonstrate vascularity, particularly valuable for haemangioma/ vascular malformations. Some typical features that may help suggesting specific entities: Cartilaginous tumours—anechoic structure: • Particularly in cartilaginous exostosis, US ideal for depiction and assessing extent as well as judging cartilaginous component of exostosis and DDx from enchondroma; difficult without plain film. • US useless in chondroma and osteochondroma when positioned within bone. Osteosarcoma—irregular structure with bony cortical defects. Ewing sarcoma—dominant periosteal reaction with paralleled echogenic structure; large soft tissue component may be present, with matric calcification and

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Fig. 17.11  Bone and soft tissue tumours. (a) Osteosarcoma: soft tissue component of a bone tumour with destruction of the cortical layer. (b, c) Pathologic fracture with neurofibroma: longitudinal (b) and (c) axial section of affected hand. (d) Eosinophilic granuloma of the skull: note bony spiculae in the soft tissue bony defect. (e) (Cartilaginous) Exostosis (+ +) with only narrow cartilaginous layer. (f) Inhomogeneous hypoechoic soft tissue tumour of deep gluteal muscle which proved to be a soft tissue sarcoma. (g, h) Septated, relatively clearly demarked tumour (g), with vivid colour signals on CDS (h), consistent with a high-flow haemangioma. (i) US appearance of osteochondroma—thick cartilaginous layer, irregular cortical margin. (j) Osteosarcoma with typical spiculae in exophytic soft tissue part of bone tumour, Codman triangle, perifocal reaction

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spiculation as well as radial vessels. Note that intraosseous or, e.g., intracranial extension not well depictable by US unless bone is destructed (Fig. 17.12). Other bone tumours (lymphoma) and metastasis only seen by US if outer ossified cortex disrupted, or with large extraosseous soft tissue component (Fig. 17.12). Muscular and cutaneous metastasis more easily detectable, difficult to classify— same approach as in any other body region (see neck chapter). Pilomatrixoma—hypoechoic, cyst-like, well-defined tumour with typical central spot like echo. “Lymphangioma” [= (veno-)lymphatic vascular malformation—the old term lymphangioma should be avoided!] multiple cystic components with thin walls, a

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Fig. 17.12  Metastasis of Ewing sarcoma in occipital skull: US visualises extracranial soft tissue component with spiculae, matrix mineralisation (a) and radiating vessels (b), but cannot access intracranial portion as shown on MRI (c)

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may contain echoes from haemorrhage (with sedimentation), some vessels in septae depictable (see Fig. 17.7c, see also chapter neck/chest/mesentery). Haemangioma and vascular malformation—more or less echogenic and homogenous tissue with varying sharpness of margins (“capillary haemangioma”); large tubular-cystiform hypoechoic structures (vessels), which may dominate picture in venous malformations; flow seen on aCDS—can be classified by spectral analysis (shunt flow? High-flow haemangioma? Low-flow angioma? Only venous flow?— potentially only reliable assessable sonographically with contrast enhanced US) (Fig. 17.11 h; see also chapter neck). Additional Imaging US may be first-line examination. Plain film + MRI (and sometimes CT) mandatory according to specific oncology protocols (extent, characterisation, staging, etc. ).

17.2 Other Small Part Applications 17.2.1 General Remarks Basically, similar rules apply as detailed above. Particularly for muscle US anisotropy phenomena have to be observed—oblique angling and tilting of the transducer may obscure the normal structure—as does to a lesser extend image compounding. For detailed analysis of muscle and soft tissue echostructure a relatively high dynamic range setting helpful. Labelling/body markers are of particular importance, also indicating transducer position—to allow for a proper interpretation particularly on follow-up or second opinion.

17.2.2 Foreign Bodies US most effective in detecting superficial or tiny foreign bodies using high-­ resolution transducers, with US stand-off pads or copious US gel. Helpful to compare first unaffected and then affected side. US Findings Depends on physical characteristics: • Metal, glass—produce reverberation echoes (comet-tail artefact) (Fig.17.13a). • Wood—acoustic shadowing (Fig. 17.13b). Note  US also used successfully to guide foreign body removal (Fig. 17.13c)—see chapter on interventional US. US also useful to judge size of foreign body, relation to other structures, or assess complications such as granuloma formation or abscesses (Fig. 17.14).

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Fig. 17.13  Foreign body. (a) Reverberation caused by a metallic foreign body (similar to needles for punctures). (b) Echogenic foreign body (wooden splinter causing acoustic shadowing) in the wrist. Note inflammatory reaction of the edematous and swollen surrounding soft tissue. (c) Subcutaneous echogenic foreign body (+ +) without shadowing, but reverberations, consistent with glass splinter (foot)

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Fig. 17.14  US convincingly displays size/length (a) and location as well as relation to surrounding structures (e.g., reaching to muscle or a compromising a vessel/nerve?) (b) of foreign body and also allows visualisation of complications such as abscess formation (c)

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17.2.3 US of “Lumps and Bumps” Many clinically unclear lumps and bumps easily assessable by US  =  “POCUS” application (see respective chapter). How: • Usually high-resolution linear transducer used—use sufficient gel, avoid too much pressure if painful or uncomfortable location, assure proper stable positioning. Helpful for initial DDx—thus definition of further management/imaging/treatment by retrieving essential early information: • • • •

DDx: cystic or solid Echostructure—favouring a certain entity? Vascularisation? In which compartment—(sub)cutaneous or deeper? affecting several layers/ compartments? • Margins—well demarked or infiltrating/diffuse? • Connection with other structure—e.g., cartilaginous part of rib, exostosis, etc. (Fig. 17.15)

17.2.4 US for Peripheral Vessels Same rules apply for US of vascular pathology as in adults and in other body areas (see chapters abdomen and neck). Except for (syndromic) malformations and posttraumatic/postinterventional findings (e.g., aneurysm, arterio-venous fistula), vessel disease much rarer than in adults (no arteriosclerosis, rare thrombosis) (Fig. 17.16). Most common applications comprise: • • • •

Thrombosis/embolus Stenosis/compression Traumatic changes such as aneurysm/dissection Vascular malformations

Additional Imaging Depends on therapeutic consequence and overall scenario—sometimes MR-angiography +/−venography, CTA (e.g., posttraumatic) or even conventional catheter angiography (e.g., pre-/peri-/postinterventional) necessary.

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Fig. 17.15  US for rib variation with cartilaginous (*) “exostosis” (a), Bump in upper arm – US reveals cartilaginous exostosis (b) (+….+) – with respective plain film (cartilaginous part not seen!) Confirmation of a palpatorily enlarged lymph node (d) – however, additionally revealing larger, ugly looking nodes (*) in deeper compartments in a child eventually diagnosed with lymphoma

17.2.5 US of the Paediatric Breast Breast tissue easily assessable by US also in childhood. Indications: Different from adults. Common queries: reason for pain or swelling, developmental changes, unclear sex definition, disturbance of puberty, gynaecomastia, etc. Normal findings—vary with age and development (Fig. 17.17). • Some breast tissue often seen in neonates, even male. • Tissue often invisible in infancy and childhood—till onset of pubarche. • Breast development first shows glandular, later fatty pattern.

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Fig. 17.16  Vascular conditions. (a) Tortuous large iliac vessels in a newborn with Klippel– Trenaunay and large vascular malformations of the respective leg, with high shunt flow. (b) CDS of the vessels reveals high velocity and turbulent flow (same patient as a). (c) Numerous large atypical vascular structures identified by CDS in the thickened and edematous soft tissues of the respective leg (same patient as in a). (d, e) Venous thrombosis: no flow on aCDS (d, longitudinal section) within stiff, incompressible vein that exhibits stationary echoes within lumen (e, axial section). (f) Femoral artery aneurysm after vessel puncture, with colour jet and high-flow velocities into the aneurysm

Various stages of breast development may physiologically exhibit some dilated or even cystiform ducts (Figs. 17.8a, b and 17.19b). Typical childhood pathology (Figs. 17.18 and 17.19): • Inflammation—nonspecific, usually a clinical diagnosis, but helpful if abscess formation occurs or is suspected (similar aspect as abscess in other body compartments). • Cyst—spectrum of fibrocystic disease. • Gynaecomastia (= temporarily excess breast tissue in males, usually a clinical diagnosis): commonly in sub-areolar region, may be asymmetric or unilateral (US usually not necessary).

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Fig. 17.17  Normal US appearance during development of breast tissue: (a) neonatal, (b) breast fed infant, (c) retromammilarily developing breast during puberty, and (d) fully developed “fatty” breast in adolescent girl

• Accessory breast tissue (US usually not necessary). • Haematoma (trauma)—appears as haematoma in other body compartments, may be confusing if within breast tissue and will change appearance over time (important to get proper detailed history!). • Fibroma/fibroadenoma (juvenile giant fibroadenoma = rare specific entity, huge, rapidly growing—although benign) rare. • Other benign tumours and respective DDx (vascular malformations = haemangioma/lymphatic malformation, intraductal papilloma/juvenile papillomatosis, stromal hyperplasia, etc.) • Malignant tumours of the breast in childhood are rarities. Additional Imaging • US usually first and only modality needed. • Sometimes MRI helpful/necessary. • Mammography hardly performed even in older childhood.

17.2.6 US of Muscles Muscle easily assessable, but proper technique and transducer choice essential for reliable results (remember, e.g., anisotropy effect causing confusion, etc.).

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Fig. 17.18  Other various typical breast US findings in childhood: (a) simple cyst (+ +, note increased through-transmission as proof of liquid nature of lesion), (b) complicated cysts with sedimentation (does not necessarily mean inflectiona), (c) subacute hematoma (d) gynecomastia, and (e) abscess

Indications/Applications Main applications: • Rupture/tear or haematoma • Inflammation/abscess • Structural changes (e.g., in various systemic diseases such as muscle dystrophy, or secondary to nerve or vascular injury, inactivity, neurologic impairment, etc.).

17.2.6.1 Traumatic Changes: Haematoma/Tear/Rupture With increasing sport activities and ambitions this query poses more often—also as consequence of excessive training/body building (sometimes without proper supervision/guidance) (Fig. 17.20). Tip  Start with healthy side to get oriented on the intraindividual normal appearance. Assess respective painful muscle area in both orthogonal axes; sometimes coronal views help to better visualise continuity of structures.

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Fig. 17.19  Breast US in childhood: (a) Neonatal breast abscess—huge collection with membrane and adjacent soft tissue reaction (hyperechoic, swelling) after neonatal mastitis; note plenty US gel to facilitate transducer coupling to tissue without interposing air. (b) Impressive cystiform duct ectasia in a breast feed infant. (c) Asymmetric prominent breast tissue at onset of pubarche in 11-year-old girl

Fig. 17.20  Extended view US depicts huge haematoma after rupture of calf muscles during body building (measurements taken, also of small complex-fluid defect)

US Findings: Swelling, changed echogenicity due to oedema, disruption of continuity, focal mass. • Most often representing haematoma –– Echogenicity of haematoma varies over time: initially echogenic to increasingly inhomogeneous and eventually hypoechoic (seroma formation). Other aspects: • Residual fibres intact? Just muscle or tendon involved? • Estimate dimension of injury: –– Possible by assuming percentage of cross-sectional area: small (70%), total rupture.

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17.2.6.2 Inflammatory Myositis As stated above, start with the healthy side to get oriented, learn intraindividual normal appearance, but also to calm patient and make child familiar with procedure—reducing fear and thus enabling assessment of potentially painful regions. Tip  For this application using not well heated US gel may be helpful. Assess respective painful area in both orthogonal axes; sometimes coronal views achievable and helpful. US Findings • Altered echogenicity of swollen and enlarged muscle, • Potentially accompanying fascial effusion, adjacent soft tissue involvement, • Sometimes hypervascularity (on CDS). US may depict necrosis or abscess formation, assess extent and define muscles involved. • Myositis ossificans: not real myositis, often posttraumatic with (secondary) calcifications (e.g., after haematoma, etc.), may mimic tumours (Fig. 17.21).

17.2.6.3 O  ther Structural Changes: Fibro-Dystrophic or Atrophic Muscles US used to recognise and differentiate muscular atrophy and changes in degenerative disease and other muscle dystrophies: • Helps differentiate thin but normal muscle from fibro-dystrophic fatty degenerated muscles –– Appear hyperechoic and less striated/structured –– Exhibit increasing distal sound attenuation. a

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Fig. 17.21  Myositis ossificans. (a) Calcified haematoma adjacent to bone. (b) Complex inflammatory reactive changes of muscle structure with liquid compartment (++) and several calcifications

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• US can help select biopsy site and improve success. • Standardised views and transducer position as well device settings are extremely important. • Potentially a future application of quantitative US-elastography. Muscular dystrophy—muscle size normal to thickened. Spinal muscular atrophy—muscles thin; affected muscle groups can be depicted helping to decide on site of muscle biopsy (to avoid non-diagnostic punctures) by defining affected muscle groups (Fig. 17.22). • Entity may be better defined even in early stages.

17.2.7 Miscellaneous Other Applications As US is easily available in many locations it will increasingly be used as a first-line imaging assessment modality, thus many appearances and entities will be encountered in superficial and small parts. Sometimes it is also essential to realise that one cannot access some areas usually well seen and then deduct the respective diagnosis from analysing possible causes and explanations, e.g., a subcutaneous emphysema (Fig. 17.23). • Some applications accounted to small part US are addressed in other chapters (e.g., US of spine and spinal canal, of lymph nodes, of the orbit, for pyloric hypertrophy or testicular US)—refer to the respective chapters. US can also be used as initial examination to the direct further diagnostic steps in clinically unclear situations (Fig. 17.24). May save your day—give it a try!

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Fig. 17.22  US in muscular dystrophy: Echogenic fibrous remnants of affected muscle (leg) in Duchenne muscular dystrophy (a). A standardised device setting essential for ­comparison and follow-up by US; image (b) nicely demonstrates the affected muscle groups

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Fig. 17.23  Subcutaneous emphysema: echogenic gas layer in subcutis, hinders sound penetration to deeper areas and causes reverberation artefacts: sometimes it is important to recognise what cannot be seen and why

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Fig. 17.24  US for troubleshooting in clinically equivocal situations: (a) Child not moving leg, plain film without any specific finding, slightly elevated inflammatory parameters: US reveals subperiosteal abscess (+ +). (b) Slightly swollen and painful leg with a history of trauma: US reveals a venous thrombosis and not a muscle tear/haematoma which was originally suspected

US of Peripheral Nerves in Childhood

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18.1 General Remarks Numerous peripheral nerves can be visualized by high-resolution US with excellent image quality. For diagnosis of various peripheral nerve lesions additional information on history, the neurological status, and nerve conduction velocity may be very important; additional nerve US may be valuable for surgical planning or for detection of tumors. Note  Knowledge of nerve anatomy = indispensable prerequisite.

18.2 US Technique Requisites: Use high-resolution high-frequency linear transducers wherever possible (with Doppler options). Small footprint transducers/hockey-stick can be helpful in neonates and infants. Color or power Doppler may provide additional information in inflammation, postoperative changes, or tumors.

J. Jüngert Department of Pediatrics and Adolescent Medicine, University Hospital Erlangen, Friedrich-­ Alexander-­Universität Erlangen-Nürnberg, Erlangen, Germany e-mail: [email protected] M. Riccabona (*) Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_18

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Tip  Avoid too much pressure, assess transverse and longitudinal plane. Usually the organo-axial approach is better and easier for initial orientation and nerve identification. Frequency: Broad-band, highest frequency at least 10  MHz. For superficial nerves 18–15  MHz, for deep nerves (e.g., sciatic nerve) 12–9  MHz. The choice depends on the anatomical region and the size of child/infant. Additional helpful techniques: Compounding/cross beam imaging, harmonic imaging, speckle reduction filters, sometimes extended field of view/panoramic imaging. Tip  Use Plenty Gel; sometimes (soft) gelpad for near-surface structures (to place focus close to surface or properly aline and couple up transducer) and for nerves running along bony edge necessary. Perform static and if required dynamic investigation—the latter helpful to differentiate nerves from moving muscles or tendons and joint structures in addition to anatomy and structure. To optimize access to nerve, cushions can be helpful to position an extremity.

18.3 Nerve Anatomy/Structure Numerous parallel fascicles of varying thickness embedded in endoneurium, each fascicle surrounded by perineurium. A single fascicle formed by several fibers. Single nerve fibers: Numerous axons, myelin sheaths, Schwann cells—the individual nerve fibers surrounded by endoneurium. The epineurium contains vasa nervorum (Fig. 18.1).

Fig. 18.1  Schematic drawing of peripheral nerve structure

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18.3.1 Normal US Findings Shape: • In organo-axial section: Round or ovoid. Note  The organo-axial section of a healthy peripheral nerve has a typical honeycomb or cable structure, provided transducer is kept orthogonal to nerve (Fig 18.2a). • Appearance in longitudinal section: Nerves appear as a hypoechoic longitudinal structure with slightly wavy hyperechoic internal structures (Fig. 18.2b). • Echogenicity variable—influenced by angle of insonation, due to anisotropy effect, as observed in any tissues composed almost entirely of strong specular reflectors like especially tendons and slightly less pronounced nerves (Fig. 18.2c). Tip  To differentiate between nerve and tendon, perform transverse and longitudinal scans, e.g., through median nerve at wrist level in B-Mode: interfaces between individual fascicular bundles inside nerve seen as continuous hypoechoic ­longitudinal elements surrounded by echoic peri- and epineurium. The adjacent tendon on the contrary shows discontinuous speckles and increased anisotropy.

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Fig. 18.2  Wrist (median Nerve)—normal findings. (a) Ultrahigh-frequency US, transverse section: nerve with hypoechoic fascicles—“cable structure” (courtesy of Dr. A.  Regensburger, Erlangen, Germany). (b) Longitudinal section: using a soft gelpad, continuous hypoechoic longitudinal structure depicted with slightly wavy hyperechoic internal structures. (c) Retinaculum (arrow), median nerve (asterisk)—hypoechoic, the adjacent tendon (arrowheads) of variable hyperechogenicity due to anisotropy. (d) Transducer position

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18.3.2 Most Important Clinical Questions in Children • Assure continuity of major nerves after trauma • Assess for iatrogenic or postoperative nerve damage. • Recognition of nerve tumors (in childhood mostly neurofibroma, schwannoma, malignant nerve sheath tumor). • Miscellaneous (e.g., in patients with spinal muscle atrophy): evaluate architecture, including fascicle number, fascicle density, and diameter/area (e.g., supplemental diagnostic option). • In individual cases: sonographically guide biopsy of neural lesions • Sonographically guide regional anesthesia. • Detect compression of nerves (rare in childhood). Note  In cases with unclear/atypical symptoms look beyond horizon, e.g., examine entire brachial plexus of affected side in addition to entire course of nerve. Also examine nerve of unaffected side (possibly as a starting point, to get familiar with the respective anatomy and appearance), also of elementary importance for intra-­ individual comparison (including evaluation of ultrastructure). Document common anatomical landmarks (vessels, articulations, or specific bony characteristics) on captured image—helpful to identify nerves.

18.4 Cranial Nerve US Some examples of nerves which may be important.

18.4.1 Optic Nerve (Cranial Nerve II) Access to optic nerve = transbulbar US. Outside ophthalmology only used for special indications, such as measurements of optic nerve sheath diameter/thickness (ONSD)—potential noninvasive parameter for evaluation of intracranial pressure, unclear orbital tumor, or tumor of optic nerve (Fig. 18.8a, b). Note  Do not press, use correct preset, reduce output power, and thus guarantee low MI (below 0.3) for B-Mode and low TI (particularly for Doppler). Shortest possible examination time, especially for premature and newborn babies (“ASARA  =  As Short As Reasonably Achievably”). Avoid Doppler with high power settings particularly in vitreous body of eye. Tip  No gel directly into eye, examine through closed upper eyelid (as for orbit US). To assess optical nerve, ask cooperative children to look straight ahead.

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18.4.2 Facial Nerve (Cranial Nerve VII) Identify after leaving outlet of temporal bone posterior to perpendicular mandibular branch. Becomes difficult/impossible after entering parotid gland.

18.4.3 Vagal Nerve (Cranial Nerve X) Best visualized at level of carotid sinus and to a certain extent along extracranial course.

18.5 Cervical and Brachial Plexus The cervical and brachial plexus can sonographically be identified best with a slight cranial tilt of transducer in transverse plane through interscalenic gap.

18.6 US of Peripheral Nerves of Extremities Some examples given as well as remarks of commonly requested examinations of peripheral nerves in extremities.

18.6.1 Median Nerve Emerges from plexus brachialis (lateral and medial fascicle). Biggest nerve of the upper arm. Ventral to brachial artery (Fig.  18.3). Distal course/wrist—see above (Fig. 18.2). a

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Fig. 18.3  US of median nerve: (a) Normal course of median nerve (red line) and ulnar nerve (black line). (b) Transverse scan: Median nerve (arrows) ventral to the brachial artery (arrowhead)

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Typical disease—Carpal tunnel syndrome: typically affecting dominant hand, manifest with pain, particularly at night – need to follow nerve down to carpal ­tunnel/wrist. • US findings: abrupt caliber change of generally enlarged nerve at entrance of carpal tunnel.

18.6.2 Ulnar Nerve Main branch of medial fascicle of brachial plexus. Heads directly downward to elbow (sulcus nervi ulnaris)—lower margin of medial epicondyle of humerus. Easy to identify (within the medial bicipital groove posterior to brachial artery, or single structure within groove of ulnar nerve) (Fig. 18.4).

18.6.3 Radial Nerve Can be seen just proximal to antecubital fossa; from there to be followed to axilla. Distally from antecubital fossa nerve splits into small branches (superficial radial and posterior interosseous nerves)—difficult to depict. Most common cause of radial nerve injury is dislocated fracture of humerus. Note  Not easily imaged by US throghout entire length of arm—unlike median and ulnar nerve.

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Fig. 18.4  US of the ulnar nerve. (a) Position of transducer—longitudinal US scan of (b) ulnar nerve (arrows) within the sulcus nervi ulnaris

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18.6.4 Femoral Nerve One of the biggest peripheral nerves, inguinally positioned—between femoral artery and iliopsoas muscle. Branches out into ventral and medial cutaneous nerve, motor branches for supplied muscles, and final branch (saphenous nerve).

18.6.5 Sciatic Nerve The biggest nerve. Can first been seen at gluteal crease. Deep location in leg. Reliably depictable several centimeters proximal of popliteal fossa—typical homogenous texture. Nerve splits distally into common peroneal and tibial nerves.

18.7 Nerve Trauma Different kinds can be differentiated (Table 18.1) • Direct: nerve directly affected • Indirect: forwarded (e.g., bruises) or associated with other injuries (e.g., bone fracture) • Primary nerve lesion = transection (Fig. 18.5) • Secondary nerve lesions = gradually developing nerve compression by scar tissue formation, e.g., bony callus or organizing hematoma. Table 18.1  Peripheral Nerve Injuries (PNI’s). Adapted from Neurotmesis CC-BY-SA-3.0-de. J. Lengerke Types of injury

Neurapraxia

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Fig. 18.5  Iatrogenic neurotmesis: 9-year-old boy after percutaneous fasciotomy of knee flexors. Unclear paralysis with loss of foot lifting and lowering, below the knee loss of sensitivity at lateral lower leg and back of foot. (a) Longitudinal section over distal femur from dorsal, cranially of sciatic nerve bifurcation in tibial nerve and common fibular nerve. Sciatic nerve (asterisk) ends abruptly (arrows). (b) In the assumed further nerve course distally note other end of sciatic nerve (arrows). (c) Inhomogeneous subcutaneous tissue and musculature after fasciotomy. Interruption of regular nerve course (distance between the two nerve ends approx. 4.3 cm, arrow) requiring surgical intervention with neural interposition

18.8 Peripheral Nerve Tumors 18.8.1 Neur(in-)oma Quite common after traumatic peripheral nerve lesions. Two possible origins: • Direct result of a trauma—partial damaged axons with consecutive axonal overgrowth (traction neuroma—hypoechoic mass inside nerve). • After surgery (Fig. 18.6).

18.8.2 Benign Peripheral Nerve Tumors US Finding Well defined mass, oval or fusiform shape, homogeneous echotexture of low or intermediate echogenicity. Note  Try to differentiate musculoskeletal lesions with secondary nerve involvement from direct nerve lesions.

18.8.3 Schwannoma Findings Solitary, plexiform, or multinodular form. True capsule, fusiform shape because of nerve entering and exiting the mass. May demonstrate high vascularity. • Degenerated Schwannoma—high amount of cystic degeneration. Calcifications or hemorrhage. • Malignant transformation extremely rare.

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Fig. 18.6  Neurotmesis with neuroma: 16-yearold adolescent with osteosarcoma, nearly 15 months after lower leg amputation. Oval hypoechoic formation at end of sciatic nerve (arrows)

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Fig. 18.7  US of schwannoma. (a) Panorama-/extended view scan shows a large inhomogeneous paravertebral tumor with connection to neuroforamen (b) exhibiting cystic areas, as well as a distinct arterial perfusion (c)

Note  Mass has eccentric location in relation to involved nerve. Helpful feature for differentiation against neurofibroma in large nerves (Fig. 18.7).

18.8.4 Neurofibroma US Findings Similar characteristics as schwannomas. Oval, hypoechoic, well defined, some are slightly ill defined. Three groups: localized, diffuse, plexiform. • Plexiform and diffuse form associated with neurofibromatosis type 1 Note  Neurofibroma can occur in any nerve and part of body including visceral organs. Only plexiform neurofibroma pathognomonic for neurofibromatosis type 1 (Fig. 18.8).

18.8.5 Nerve Sheath Ganglion Non-neural (pseudo-) tumor within nerve sheath. Arise from joint, not from nerve— joint fluid leaks into nerve sheet.

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Fig. 18.8  Neurofibromatosis type 1. (a, b) Transbulbar sonography: Considerably thickened optic nerve. (c) Nine-year-old girl, sagittal midline section in lower pelvis: Large retrovesical tumor with nodular formation, corresponding to neurofibromas (arrows). (d) Neurofibromas in thigh along sciatic nerve Fig. 18.9  Malignant nerve sheath tumor located adjacent to left mandible. Note small hyperechoic spiculae corresponding to calcifications, similar to osteosarcoma or Ewing sarcoma

• Rare in children, observed, for example, as peroneal intraneural ganglion cyst. Sometimes associated with palpable mass can arise in other regions, too (e.g. wrist ...). • Can cause of pain, foot drop, and common peroneal nerve symptoms. Via an articular branch of common peroneal nerve at proximal tibiofibular joint fluid may extend under pressure from knee joint into tibiofibular joint and subsequently into common peroneal nerve sheath. US Appearance Anechoic, often multilocular fluid collection, adjacent to and along nerve; e.g., along course of common peroneal nerve with extension into sciatic and tibial nerve sheet.

18.8.6 Malignant Peripheral Nerve Tumors Arise from sheath, fibroblasts, or perineural cells. Mainly affect major nerve trunks. Grow fast, usually large in size at diagnosis. US Findings Based purely on gray scale US distinction impossible—except for invasive growth as typical malignant feature (Fig. 18.9).

Part IV Miscellaneous

US-Guided Interventions and Invasive US Procedures and Respective Follow-Up

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Brian Coley, Gerolf Schweintzger, and Michael Riccabona

19.1 General Aspects US used to plan, guide and monitor all kinds of invasive and interventional procedures. Specific handling and equipment may be necessary, as well as training and experience. US may also serve for follow-up afterwards or for assessing complications. Many applications, increasing importance—as US ideal for guiding and monitoring procedures: • Particularly in superficial structures and in children (radiation protection issues!). Typical Interventions/ Indications in childhood: • • • • •

Reduction of intussusception or meconium plug. Genitography and ce-VUS (see respective chapters, too). US-guided reposition (e.g. epiphysiolysis)—not further discussed. Biopsies (e.g., suspected tumours or parenchymal disease). Aspiration and drainage (abscess, fluid collections and effusions, etc.).

B. Coley (*) Department of Radiology, ML5031, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA e-mail: [email protected]; [email protected] G. Schweintzger Abteilung für Kinder und Jugendliche Neonatologische und padiatrische Intensivstation, LKH Leoben/Eisenerz, Leoben, Austria e-mail: [email protected] M. Riccabona Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_19

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• Vascular access. • Sclerotherapy (venous and lymphatic malformations). • Foreign body removal.

19.1.1 Requisites Select adequate transducer for target/organ: • High-resolution linear transducer for superficial structures (sometimes hockey stick helpful). • Curved arrays for deep targets. • Frequencies vary, respectively.

19.1.2 Other Important Needs High frame rate is helpful; CDS is helpful for many procedures. Cine-loop documentation recommended—still images taken retrospectively from stored loops. Core biopsy or cytology aspiration needles used—depending on target and necessary material. Needle guide sometimes helpful—must fit selected transducer (check in advance, also fitting needles). Biopsy gun or similar, partially semi-automated devices.

19.1.3 Precautions and Preparations • Proper preparation essential for success. • Initial assessment, informed consent, discussion with clinician, laboratory assessment, time out. • Sterile conditions have to be maintained (except for saline enema): –– Sterile cover for transducer (and US keyboard if no assistant), sterile needle guide (if used), antiseptic skin cleanser and sterile cloths/drapes to cover surrounding area. • Important for both patient and operator to be positioned comfortably. • Monitoring + resuscitation equipment must be present and readily available. • Analgesia and sedation—in children procedures are often performed under general anaesthesia or conscious sedation—coordination with other providers is mandatory. Tip  Place local anaesthetic paste at area of access well in advance. • Prepare catheters, lines, tubes, materials for sample handling and all other supplies well before; use standardised checklist.

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• If possible, have an interventional suite equipped with all necessary material and devices including adequate transducers, potentially needle guide. • Needle guides less frequently used/cumbersome in small and superficial structures. –– for this freehand technique is usually preferred. • Guide (and coaxial technique) more frequently used/advisable for deeper structures. • Proper instruments readily available. • Needles of various sizes and length, catheters, medications, fixation devices, haemostat, etc. • For biopsies: specimen-handling needs, pathology support. • Interventional procedures require a team approach—establish an interventional team with clear structure and duties/responsibilities. • Pre-procedural assessment of case with definition of access needs, needle size and calibre and kind of approach (needle guide versus freehand approach, coaxial technique or single needle, etc.) is recommended. • Have microscope available for immediate inspection—helps to avoid unnecessary passes or unsuccessful biopsies. Useful to ask patient to empty bladder before procedure (exception: saline enema, US genitography). • If you consider using ultrasound contrast agents (UCA), get informed consent and prepare materials. • Monitor and document entire procedure. • Post-procedural check and follow-up. Practical Tips • Use highest-frequency transducer that allows visualisation of target lesion. • Set focal zone at target, try to access in tilted plain to receive reasonable echoes from needle to observe track.

19.2 U  S-Guided Filling of Structures for Diagnostic or Therapeutic Purpose 19.2.1 General Remarks for Assessing Physiologic Cavities (For Example, Bladder, Vagina, Intestines, Stomach, etc.) Filling of structures with saline (or tea/formula for stomach) is very helpful—e.g. to replace air, for distension: • Additionally UCA can be added for improved depiction of various phenomena (e.g. reflux, fistulae, communication of different cavities). • Filling usually needs catheter—except for upper intestines where fluid can be ingested. Tip  Flush catheter with fluid before insertion (to avoid infusing air which might obscure findings and impair visualisation).

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• All investigations need justification but often can help to replace other invasive methods using radiation. • Consider sedation (rectally/orally) in anxious children—as proposed for VCUG (e.g. midazolam, chloral hydrate).

19.2.2 Diagnostic Sonographic Enema Usually no precautions are necessary unless evaluating potential polyps—then evacuation by conventional enemas before investigation is helpful. Indications: Unclear large bowel findings—particularly stenosis, polyps, unclear tumorous lesions, suspected fistula tracts, equivocal suspicion/US findings (intussusception, meconium plug, small left colon, megacolon, etc.). How to do: • Rectal tube/catheter inserted—use flexible tubes to prevent perforation, particularly risky in preterm neonates. • Tube is gently inserted after lubrication—in neonates under constant saline infusion until well positioned; try to insert at least to the height of recto-sigmoid junction. • Tube taped or well-fixed manually to prevent early fluid evacuation and dislocation (particularly useful in older children)—particularly important for bowel ­distention to depict stenosis or dilatation and to judge colon diameter (e.g. small left colon, etc.). Tip  Drip infusions preferred where height of infusion bottle can be used as manometer to avoid overly high pressures; rarely gentle injection by syringe can be an alternative option, mostly for therapeutic approaches. Saline should be pre-warmed. • After starting enema, US surveillance of gradual filling of recto-sigmoid, then descending colon, left flexure, transverse colon and eventually ascending colon + coecum. Always monitor by US (Fig. 19.1). Fluid influx into distal ileum and fluid distension of appendix are often seen. • Tube removed after sufficient filling and distention of entire colon, assess in longitudinal + axial sections. • Perineal US can be applied to observe defaecation, particularly observe shape of rectum and transition zone to anal canal as well as respective angulations secondary to pelvic floor activity after withdrawing the catheter (Fig. 19.2). • In unclear situations, particularly for depiction of fistulae, UCA may be added (see chapter on ce-US).

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Fig. 19.1  Diagnostic US saline enema. (a) Tube inserted, colon filled and distended with saline. (b) Increasing filling of more proximal bowel loops after advancing tube under constant saline irrigation. (c) The soft feeding tube advanced further—no distension can be achieved, no saline passes to more oral loops, no meconium plugs seen at that level—indicative for atresia

Fig. 19.2  Perineal US for defaecation. (a) Perineal US demonstrates bladder, urethra, narrow and atypical anal canal and fluid-filled rectal pouch. Note no distal opening of the anus and no proper anal canal in a neonate with anal atresia. (b) Still image from a video clip during defaecation after saline enema, perineal sagittal view (neonate): open short rectal canal, atypical shape of recto-­ pubic angle

19.2.3 Therapeutic Sonographic Enema Same procedure as above using higher filling pressures can be used for reduction of intussusception or meconium plug. How to do: Basically same technique as described above: • Dedicated precautions are recommended: analgesia/sedation, IV infusion for hydration and electrolyte balance in intussusception, sometimes antibiotic prophylaxis, physiological monitoring.

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• For successful reduction of intussusception, higher pressures must be applied, thus larger tubes are necessary. Filling pressure = 80–100 cm H2O (less in preterms/neonates): –– Success is seen if saline enters beyond point of obstruction: in intussusception unhindered reflux into ileum is mandatory; in meconium obstruction, mixing of meconium with saline and mobilisation of plugs indicates success and rules out atresia at that level (Fig. 19.3). –– Repeated attempts after a pause can be performed and may increase success rate, also some bowel massage may be helpful. • Mandatory to seal anal canal by taping or manual compression; use of balloon catheters not recommended due to higher risk for perforation during uncontrolled pressure increase. Benefits: Easily repeatable, furthermore, guided by US manual/transducer massage can assist reduction in intussusception or mobilisation of meconium; procedure applicable at bedside. Some only massage the intussusceptum out of the intussuscipiens manually through the abdominal wall (using same technique as surgeons would intra-operatively) without the enema procedure, with some reported success.

Fig. 19.3  Therapeutic saline enema: reduction of intussusception (or meconium ileus). (a) Typical US image of intussusception (with entrapped fluid). (b) Enema fluid starts to push back the intussusception, enema fluid (saline) filling of colon from saline enema (80 cm water pressure). (c, d) Gradually fluid is reducing the intussusception, increasing fluid around head of invaginated bowel. (e) Intussusception successfully reduced—fluid passes through somewhat swollen ileocoecal valve. (f) Enema has reached small bowel which is filled with enema fluid from now unhindered reflux into ileum

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Restrictions: Less anatomic overview; fluid instead of air (as used for pneumatic reduction)—less elastic—higher perforation risk.

19.2.4 US Genitography Indications: Equivocal findings on US or dedicated query “suspicion of genital malformation”. How to do: With full bladder (or after filling of bladder), vagina filled after gentle catheterisation. Filling with saline or with UCA (as described for ce-VUS, may be added later if required—e.g. for depiction of communications or fistulae). Same saline infusion technique with constant drip and pre-filled catheter as for ce-VUS (see below, Sect. 19.2.5 and chapter on ce-US), possibly combine with voiding cycle of ce-VUS (e.g. urogenital sinus tract—always flow from higher pressure to lower pressure system—thus fistula may fill only during voiding): • Distension, size/shape of vagina clearly delineated, potential fistula visible, atretic/double vaginas, cysts, uterine cervix much better delineated; improves assessment of uterine malformations (Fig. 19.4). • 3DUS with coronal reconstructions helpful and improves classification particularly of uterine malformations (see respective chapter with figures). • Perineal approach + complementing upper abdominal/urinary tract study added (Fig. 19.5 and respective chapters). • Eventually catheters removed, vagina observed during/after voiding for urine influx into vagina. • In case of suspected fistulae—additional instillation of UCA to enhance structures/clearly delineate connection between different cavities. UCA may improve visualisation and DDx (see also chapter on ce-US).

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Fig. 19.4  US genitography. (a) Axial transvesical section: vagina with catheter during filling with saline infusion for US genitography. (b) Longitudinal transvesical view: nicely outlined uterine cervix after distension and filling of vagina via saline infusion. (c) ce-US genitography: additionally diluted UCA added to see if there is a connection between the two vaginas in a girl with uterus didelphis and hydrocolpos of atretic hemivagina; no contrast seen in right-sided cystic-obstructed hemivagina, normally filled and distended echoic contrast-filled main left vagina (double image technique, left side is dedicated contrast image, right lower box/side is fundamental image)

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Fig. 19.5  Perineal US for vaginal pathology after filling with saline/during voiding. (a) Vagina filled with saline after catheter is withdrawn, cervix lips nicely visualised. (b) Perineal sagittal US depicts an obvious fistula (+ +) to urine-filled distended vagina. (c) Additional diluted UCA instillation (ce-VUS + ce-US-genitography) demonstrates intact vagina and separated course of urethra (during voiding) and vagina. (d) Distal common tract of urethra and vagina (urogenital sinus tract) depicted on ce-US genitography by sagittal perineal access during voiding in a newborn girl with adrenogenital syndrome

19.2.5 Contrast-Enhanced Voiding Urosonography (ce-VUS) Definition US method for detection of vesico-ureteric reflux (VUR)—see also respective chapters. UCA has been recently licensed for paediatric use also in Europe, and up to now thousands of investigations have been performed—high success rate, low complication rate and reliable results well documented (see Fig. 4.1 in respective chapter = old 2.6). Indications: Recommended in girls and for follow-up investigations, as well as for family screening. With increasing ability to properly assess urethra also applicable to male infants. Particularly valuable in dilated systems—more sensitive towards VUR as there is no dilution effect as in VCUG. Note  Initial thorough detailed comprehensive US investigation of entire urinary tract including post-void assessment mandatory before performing ce-VUS. Diagnosis: Any UCA in upper urinary tract/ureters seen as echogenic bubbles— indicative of VUR (Fig.  19.6). Also try to note potential CA influx into vagina. Establish grading related to international VUR classification system (see Table 4.1 in respective chapter). Remember to try to assess urethra during voiding using a perineal or transsymphysic access (see respective chapter with figures, too). Benefits: Higher VUR detection rate, no radiation, additional information on non-refluxing structures and soft tissues, bedside applicability, etc. Limitations: Difficult handling for visualisation of urethra. Must have sonographic access to kidneys, bladder and distal ureter area (limited, e.g. in severe scoliosis). Restrictions in visualisation of late, low-degree, high-pressure VUR at end of voiding (no US access, as bladder is nearly empty), limited depiction of intermittent diverticulae (for same reason). No panoramic overview. No clear delineation of entire ureteral anatomy—therefore preoperatively always perform conventional fluoroscopic VCUG.

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Fig. 19.6  Typical renal appearance of VUR on ce-VUS. (a) Dual image technique (left—contrast image): contrast has refluxed into kidney’s collecting system, with echogenic contrast-filled pelvo-­ caliceal system. (b) Dual image technique (left—contrast image): slightly dilated collecting system filled with UCA—not depictable on basic B-mode images without contrast detection settings

Note  ce-VUS tends to grade VUR slightly higher, particularly VUR I° on VCUG often seen as VUR II° on ce-VUS. Modern UCA visualisation techniques using low MI imaging preferred, as UCA stays stable much longer and VUR depiction improved.

19.2.6 Other Intracavitary Contrast Applications Saline and UCA can be applied to any other cavity such as assessment of drains (position and function), lines (patency), abscesses and collections (fistulae?). Same principle and concentration apply as above. UCA concentration varies with agent, for SonoVue (Bracco, Italy—the most commonly used agent) approx. 0.2–1% solution. For more details see chapter on ce-US.

19.2.7 Intravenous ce-US Increasingly advocated in children in spite of lack of approved UCA (only recently Lumason®/Bracco, Italy licensed for use in paediatric liver in the USA). Only rarely severe side effects reported in young children. Same principles apply as in adults. See also respective chapter. Indications: • Visualisation of flow + vessels under poor scanning conditions/insonation angle (deep structures, transcranial, etc.), assessment of vessel patency. • Detection of parenchymal lesions (neoplastic, infectious, after trauma, etc.) (Fig. 19.7). • Lesion characterisation by using specific perfusion patterns (as known from CT/ MRI), particularly in liver (Fig. 19.7, also see Fig. 4.6, 4.7, and Table 4.2). • Assessment of perfusion in small peripheral areas, difficult to depict and assess with conventional Doppler (joints, bowel wall, potentially also testis, etc.)— these applications are not well established, use caution due to potential harm by cavitation effects. For further details see chapter on ce-US.

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Fig. 19.7  Dynamic CEUS in a liver lesion. (a) Unenhanced US shows two round liver lesions in a girl with a fatty liver. (b–e) Serial images during CEUS (dual image technique, left—contrast image), same patient as in a: early vascular/arterial enhancement of spoke wheel-like central vessels in the tumour, with increasing pronounced enhancement of the lesions till portal phase—eventually homogenous enhancement of the lesion same as the surrounding liver in the late phase, consistent with FNH (focal nodular hyperplasia)

19.3 Biopsies and Punctures Most common biopsy targets: Liver/kidney, rarely nodes, suspected tumours/unclear masses and collections. How to do: • Initial pre-interventional US must be comprehensive and detailed—properly assess anatomy and discover potential contraindications to US guidance. • Preparation as described above (Sect. 19.1.2). • For diffuse pathology (mostly liver): easily and safely accessible part of representative parenchyma chosen, access usually from ventral or ventrolateral (liver). Multiple semi-automated and manual core biopsy devices available (Fig. 19.8a, b).

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Fig. 19.8  Liver (image a, b) biopsy in a teenager with unexplained elevation of liver enzymes and node sampling (c). (a) Longitudinal US of right hepatic lobe: 16G biopsy needle with tip just under liver capsule. (b) After “firing” biopsy device, needle tip now seen deeper within hepatic parenchyma. (c) US-guided node biopsy using a cutting needle in a child with persistent cervical adenopathy focusing an enlarged hypoechoic lymph node. A 21G cutting needle passed through node with tip seen at far margin. The open specimen tract of cutting needle (arrowheads) clearly in centre of node, outer cutting cannula visible (arrow)

Fig. 19.9  Renal biopsy. (a) US at start of renal biopsy (dorsal longitudinal image): the needle tract outlined by dotted lines when using a guiding device; the distances (until reaching kidney, depth of parenchyma till reaching central structures, + +1/2) measured for selecting the proper needle size. (b) Needle tip placed just at the renal outer border, before firing the biopsy gun. (c) Needle monitoring during biopsy (image taken from a cine-loop clip): needle tip avoids central structures

• For renal biopsy, lower pole of kidney with dorsal approach commonly recommended, (cutting) needle direction steered towards area without major vessels, biopsy depth defined to avoid pelvo-caliceal system (Fig. 19.9). • Biopsy of focal lesions: commonly performed with freehand approach, though sometimes needle guides maybe helpful and improve accuracy. Most important in biopsy of suspicious nodules: maintenance of safe access without upgrading tumour by passing through unaffected compartments (talk to surgeons and oncologists before procedure); coaxial technique often helpful particularly if target positioned deeper, if multiple biopsies will be taken, or if tract needs to be embolised due to bleeding concerns. Often cutting needles used to yield sufficient tissue (Fig. 19.9c).

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Fig. 19.10  Splenic biopsy with coaxial technique and tract embolisation. (a) US of spleen in leukaemia and fevers—dominant hypoechoic mass, multiple smaller lesions. (b) A 17G guiding cannula placed into spleen (arrowhead) and an 18G biopsy needle (arrow) guided to edge of largest mass. (c) After firing biopsy device, needle traverses lesion—needle tip (arrow) seen on the far side of the mass. (d) After biopsy, Gelfoam pledgets placed through guiding cannula to prevent bleeding—seen as very bright echogenic structure (arrowheads) due to entrapped air in material

• Needle length/size varies with application: in general, small needle size has less risk of complications or bleeding but may need coaxial technique for unhindered access without distortion/twisting of needle. Furthermore—particularly in oncologic procedures—smaller needles may not yield enough tissue for necessary analysis, thus larger needles/repeated sampling may become necessary. Most commonly 18–20 gauge is sufficient, rarely 14 gauge. Coaxial technique allows embolisation of biopsy tract (using gelfoam, fibrin glue or other agents) to minimise bleeding complications, particularly in risky targets (e.g. spleen) (Fig.19.10). • Most commonly a biopsy gun or semiautomatic device is used—must become familiar with device before using it clinically. Make sure that appropriate guiding needles, etc. are available. • Always monitor intervention by US, potentially by documenting video clips (see Fig. 19.10). • Consider first proceeding only to margin of target and only then retrieve sample from tissue using biopsy device. • Most commonly core biopsies obtained; sometimes aspiration for cytological assessment sufficient. • Always send specimen or aspirated fluid for histology or laboratory/microbial workup. Make sure that specimen transport is well organised, and specimen kept under appropriate conditions. After every procedure: • Check for potential complications, e.g. disruption or bleeding (Fig. 19.11). • Particularly in areas/organs/clinical situations with high risk of complications or bleeding: consider repeat follow-up at around 3–8 and 12–24 h. • Always use CDS to examine for potential arteriovenous fistula, etc.

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Fig. 19.11  Complication of renal biopsy. (a) Dorsal longitudinal image: haematoma around lower pole of left kidney after renal biopsy. (b) aCDS improves early depiction of perirenal haematoma which may initially appear isoechoic to renal cortex. (c) Post-biopsy arteriovenous fistula depicted by CDS (arrow), confirmed by duplex analysis

19.4 Drainage Same principles apply as above. Access similar for drainage or puncture. How to do: Basically two techniques available (Fig. 19.12). 1. Trocar technique: relatively large needle with central perforation used to access collection of fluid-filled structure; drain then inserted through central lumen of needle. Alternatively, drain with inner trocar advanced directly into collection, and drain deployed. 2. Seldinger technique: small needle used to access collection, guide wire placed, tract dilated and then drainage catheter inserted—less traumatic for tissue but more cumbersome; may need fluoroscopy to visualise proper wire placement and safe handling during dilatation and drain insertion. Note  After successful drainage, always assure proper placement of catheter tip and proper function (Fig. 19.13, see also 4.1)—postinterventional US check recommended. Needle/tube size: Depends on location, patient size/age and composition of aspirated fluid: • Larger bore drains (8–16 French) necessary in complicated or septated collections (e.g. abscess, pleural empyema). • Smaller bore drains—used for clear fluid (e.g. 5 or 6 French for infant urinary drainage). • If instillation of sclerosing/therapeutic agent considered, particular precaution has to be taken to avoid leakage of injurious agent—sometimes combined fluoroscopic-­sonographic access with CM instillation to clearly demonstrate absence of fistulae or leak may be necessary. • CT: more reluctantly used to guide procedures in children due to radiation burden, however, helpful alternative (as is sometimes fluoroscopy) if US cannot grant safe access or sufficient visibility of access pathway and target/structure.

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Fig. 19.12  Schematic drawing demonstrates the two common puncture techniques: Seldinger (a) and trocar (b). (a) Seldinger technique: system accessed with thin needle; guide wire placed through narrow needle lumen to secure access. Then dilatators used to widen access tract, before eventually catheter passed over guide wire. (b) Trocar technique: large needle (trocar) introduced—has wide lumen that allows placing of catheter through lumen of this access needle—usually no guide wire needed, often preferred for US (as handling and visualisation by US are easier, less need for complementing fluoroscopy, etc.)

Fig. 19.13  US-guided abscess drainage (Seldinger technique) in perforated appendicitis. (a) Longitudinal US shows large abscess (A) below liver (L). (b) Small aspiration catheter (arrowheads) placed into collection below liver edge. (c) Guide wire (arrowheads) passed into deepest part of collection in Morrison pouch, then 12F drainage catheter placed over guide wire to drain abscess

19.5 Vascular Access US can be used to guide puncture of vessels after demonstrating their patency, not only at site of puncture but also further downstream by either following vessel or indirectly by proving normal flow profiles. How to do: Usually freehand technique better, but avoid high transducer pressure which might compress vessel lumen complicating successful puncture: • Positioning manoeuvres sometimes helpful to properly fill vessel. After needle insertion guide wire is placed and catheter is advanced per standard techniques.

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• Low angle between transducer surface and needle path improves needle visibility—decision on axial versus longitudinal view depends on personal preference/ handling options/location and size (Fig. 19.14). • Always assure proper position at end of procedure: that catheter lies within vessel lumen, that the tip is placed appropriately and that the line functions properly. • US also used to assess tip of catheters placed without US guidance, catheter-­ related vascular complications (such as catheter-induced thrombosis) or complications of other drainage tubes, feeding lines, etc. (Fig. 19.15). Assessment of catheter tip sometimes difficult—radiograph or fluoroscopy may become necessary.

Fig. 19.14  US-guided vascular access. Longitudinal US of basilic vein shows 21G needle with tip within vessel lumen

Fig. 19.15  US for catheter/tube position. (a) Thick femoral catheter placed for ECMO ending in proximal iliac vein. (b) CDS demonstrates high flow and patency of the catheter. (c) Malposition of an umbilical vein catheter in the venous sinus (arrow)—obviously ductus venous too narrow to be passed. (d) Malposition of gastric feeding tube in a neonate—its tip is seen in the retroperitoneal para-oesophageal soft tissue adjacent to pre-vertebral aorta. (e) After instillation of new tube tip (arrow) now seen correctly placed in stomach filled with saline

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Fig. 19.16  US for lumbar puncture. (a) Longitudinal US in an infant after failed blind lumbar puncture attempts. Thecal sac (T) below conus medullaris (C) completely decompressed—with no cerebrospinal fluid seen around nerve roots of cauda equina in collapsed thecal sac. Echogenic dura (arrowheads) surrounded ventrally and dorsally by complex hypoechoic material representing haematoma and leaked CSF. (b) Longitudinal US in an infant with fever: echogenic 22G spinal needle passing between hypoechoic cartilaginous spinous processes (P)—needle tip (arrowhead) within thecal sac

19.6 Lumbar Puncture Usually done without any image guidance. In complicated cases (e.g. after unsuccessful attempts), US may be helpful to show cause or consequences of unsuccessful attempts (Fig. 19.16). US may guide needle to area where CSF can be tapped successfully (may be at higher or lower level than performed clinically) (Fig. 19.16b). US technique: Same as for diagnostic spinal US, although useful to have patient semi-upright for lumbar puncture. Tip  US also used to locate dorsal processes for counting vertebral bodies, e.g. in obese patients.

19.7 Foreign Body Removal US ideal to localise foreign bodies (see chapter on small part and MSK ultrasound). How to do (Fig. 19.17): • • • •

Localisation using high-frequency transducer. Proper/extensive local anaesthesia helps to outline foreign body. Small incision. Small haemostat inserted towards foreign body with closed teeth under US monitoring. • With gentle opening foreign body is grabbed—then slowly removed. • Thereafter rescanning is essential—ensure complete removal of foreign body. Alternative: US can be used to localise foreign body and mark it by guide wire to enable conventional surgical retrieval. May sometimes need fluoroscopic support, if poorly accessible or visible by US.

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Fig. 19.17  US-guided foreign body removal. (a) US of lower extremity shows (echogenic) piece of glass in the soft tissues. (b) With US guidance, needle directed along planned path of foreign body removal, local anaesthetic placed. (c) The haemostat jaws seen to be surrounding the foreign body, after which it was gently grasped and removed

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Fig. 19.18  US-guided local anaesthesia for paracentesis: (a) Needle approaching liver capsule (arrow). (b) Lidocaine delivered forming a deposit (arrow) next to peritoneum/liver capsule. (c) Paracentesis needle (arrow) passing through anaesthesised area

19.8 US Guidance for Local Anaesthesia US used to localise nerves or other relevant structures (liver or kidney capsule, peritoneum, etc.) to properly place anaesthetic drug and hinder nerve injury during local anaesthesia. How to do: • Localise nerve/nerve bundle, using reference structures (see also chapter on US of peripheral nerves), or other targeted structure as listed above. • Guide needle tip to respective space. • Observe deposition of drug during/after injection (Fig. 19.18), before then monitoring the procedure itself (e.g. guided puncture or biopsy, etc.).

Normal Values as Relevant for Paediatric US

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Michael Riccabona, Brian Coley, Martin Köstenberger, Hans-Joachim Mentzel, and Gerolf Schweintzger

20.1 Introduction Normal values are important, particularly in paediatric US, as children grow and all measurements (e.g. length/size/distance, ratios, volume, flow velocities, and Doppler indices, etc.) vary and change with age or size or weight during growth. Details on how to measure and what to consider (including pitfalls and restrictions) are given in the respective chapter as well as the various organ chapters; quite some tables listed in this comprehensive summary overview can also be found in the respective organ chapter.

M. Riccabona (*) Department of Radiology, Division of Pediatric Radiology, Medical University Graz and University Hospital Graz, Graz, Austria e-mail: [email protected] B. Coley Department of Radiology, ML5031, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA M. Köstenberger Division of Pediatric Cardiology, Department of Pediatrics and Adolescent Medicine, Medical University Graz and University Hospital LKH Graz, Graz, Austria H.-J. Mentzel Section of Pediatric Radiology, Institute of Diagnostic and Interventional Radiology, University Hospital Jena, Jena, Germany G. Schweintzger Abteilung für Kinder- und Jugendheilkunde, Neonatologische und padiatrische Intensivstation, LKH Hochsteiermark, Leoben, Austria © Springer Nature Switzerland AG 2020 M. Riccabona (ed.), Pediatric Ultrasound, https://doi.org/10.1007/978-3-030-47910-7_20

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20.2 Normal Values in Paediatric Neurosonography Ventricular and cerebellar size are practically the only measured anatomic structures (diameter, circumference—see also respective chapter) (Fig. 20.1 and Table 20.1); the diameter of the lateral ventricle is deemed normal postnatally as long as it is less than 10 mm (in older children with clinical signs of increased brain pressure up to 15 mm) measured at the level of the foramen of Monro; rarely other measurements are used. Some also measure the sinucortical (sagittal sinus to cortex) width as an indicator for the size of the extra-axial CSF space which is