RadCases Plus Q&A Pediatric Imaging E-Book

Richard B. Gunderman

• Herausgeber: Thieme Medical Publishers
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2019

Beschreibung

Important pediatric radiology cases and board-type Q&A review to help you pass your exam!

Pediatric radiology provides an opportunity to care for perhaps the most vulnerable patients of all, from prenatal life through adolescence. Pediatric Imaging, Second Edition by Richard Gunderman and Lisa Delaney features 100 new cases along with two board-type multiple-choice questions for each. A wide spectrum of cases focusing on radiology in children – from basic to advanced – are strategically designed to increase a resident's knowledge and provide robust exam preparation. For maximum ease of self-assessment, each case begins with the clinical presentation on the right-hand page; study that and then turn the page for imaging findings, differential diagnoses with the definitive diagnosis, essential facts, pearls and pitfalls, and more.

Key Highlights

• Multiple images for every case demonstrate how a condition appears in different modalities
• Easy-to-read bulleted formatting and concise, point-by-point presentation of the Essential Facts enables learning and retention of high-yield facts and skill-building in radiologic diagnosis
• Online access to additional cases enables residents to arrange study sessions, quickly extract and master information, and prepare for theme-based radiology conferences

Thieme's RadCases means cases selected to simulate what you will see on your exams, rounds, and rotations. RadCases helps you to identify the correct differential diagnosis for each case, including the most critical. The series comprehensively covers the following specialties:

• Breast Imaging · Cardiac Imaging · Emergency Imaging · Gastrointestinal Imaging · Genitourinary Imaging · Head and Neck Imaging · Interventional Radiology · Musculoskeletal Radiology · Neuro Imaging · Nuclear Medicine · Pediatric Imaging · Thoracic Imaging · Ultrasound Imaging

This RadCases book comes with a code providing access to additional online cases: 100 in this book plus 250+ more cases and interactive Q&A.

Master your cases, pass your exams, and diagnose with confidence: RadCases!

This print book includes complimentary access to a digital copy on https://medone.thieme.com.

Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product.

Leseprobe

To access the additional media content available with this e-book via Thieme MedOne, please use the code and follow the instructions provided at the back of the e-book.

RadCases Plus Q&A Pediatric Imaging

Second Edition

Authored by

Richard B. Gunderman, MD, PhD, MPH

The John A. Campbell Professor of Radiology

Chancellor’s Professor of Radiology, Pediatrics, Medical Education, Philosophy, Liberal Arts, Philanthropy, and Medical Humanities and Health Studies

Indiana University

Indianapolis, Indiana

Lisa R. Delaney, MD

Assistant Professor

Department of Radiology

Indiana University School of Medicine

Indianapolis, Indiana

Series Editors

Jonathan M. Lorenz, MD, FSIR

Professor of Radiology

Section of Interventional Radiology

The University of Chicago

Chicago, Illinois

Hector Ferral, MD

Senior Medical Educator

NorthShore University HealthSystem

Evanston, Illinois

370 illustrations

ThiemeNew York • Stuttgart • Delhi • Rio de Janeiro

Executive Editor: William LamsbackManaging Editors: J. Owen Zurhellen IV & Kenneth SchubachEditorial Assistant: Holly BullisDirector, Editorial Services: Mary Jo CaseyProduction Editor: Teresa Exley, Absolute Service, Inc.International Production Director: Andreas SchabertEditorial Director: Sue HodgsonInternational Marketing Director: Fiona HendersonInternational Sales Director: Louisa TurrellDirector of Institutional Sales: Adam BernackiSenior Vice President and Chief Operating Officer: Sarah VanderbiltPresident: Brian D. ScanlanPrinter: King Printing

Library of Congress Cataloging-in-Publication Data

Names: Gunderman, Richard B., editor. | Delaney, Lisa R., editor.

Title: RadCases plus Q&A pediatric imaging / edited by Richard B. Gunderman, Lisa R. Delaney.

Other titles: Pediatric imaging (Gunderman) | RadCases plus Q and A pediatric imaging

Description: Second edition. | New York : Thieme, [2019] | Series: RadCases | Preceded by Pediatric imaging / edited by Richard B. Gunderman, Lisa R. Delaney. 2010. | Includes bibliographical references and index. | Identifiers: LCCN 2018038407 (print) | LCCN 2018038630 (ebook) | ISBN 9781626235205 | ISBN 9781626235199 | ISBN 9781626235205 (e-ISBN)

Subjects: | MESH: Diagnostic Imaging | Child | Infant | Case Reports

Classification: LCC RJ51.D5 (ebook) | LCC RJ51.D5 (print) | NLM WN 240 | DDC 618.92/00754—dc23

LC record available at https://lccn.loc.gov/2018038407

Copyright © 2019 by Thieme Medical Publishers, Inc.Thieme Publishers New York333 Seventh Avenue, New York, NY 10001 USA+1 800 782 3488, [email protected]

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ISBN 978-1-62623-519-9

Also available as an e-book:eISBN 978-1-62623-520-5

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Dedicated to Laura, Rebecca, Peter, David, and John.

– RBG

Dedicated to Jill Voltmer and Ashley Carman, whose selflessness forever changed our lives and can never be repaid. We will never take for granted what you did for us.

– LRD

Contents

Series Preface

Preface

Acknowledgments

Case 1

Case 2

Case 3

Case 4

Case 5

Case 6

Case 7

Case 8

Case 9

Case 10

Case 11

Case 12

Case 13

Case 14

Case 15

Case 16

Case 17

Case 18

Case 19

Case 20

Case 21

Case 22

Case 23

Case 24

Case 25

Case 26

Case 27

Case 28

Case 29

Case 30

Case 31

Case 32

Case 33

Case 34

Case 35

Case 36

Case 37

Case 38

Case 39

Case 40

Case 41

Case 42

Case 43

Case 44

Case 45

Case 46

Case 47

Case 48

Case 49

Case 50

Case 51

Case 52

Case 53

Case 54

Case 55

Case 56

Case 57

Case 58

Case 59

Case 60

Case 61

Case 62

Case 63

Case 64

Case 65

Case 66

Case 67

Case 68

Case 69

Case 70

Case 71

Case 72

Case 73

Case 74

Case 75

Case 76

Case 77

Case 78

Case 79

Case 80

Case 81

Case 82

Case 83

Case 84

Case 85

Case 86

Case 87

Case 88

Case 89

Case 90

Case 91

Case 92

Case 93

Case 94

Case 95

Case 96

Case 97

Case 98

Case 99

Case 100

Case Questions and Answers

Further Readings

Index

Series Preface

As enthusiastic partners in radiology education, we continue our mission to ease the exhaustion and frustration shared by residents and the families of residents engaged in radiology training! In launching the second edition of the RadCases series, our intent is to expand rather than replace this already rich study experience that has been tried, tested, and popularized by residents around the world. In each subspecialty edition, we serve up 100 new, carefully chosen cases to raise the bar in our effort to assist residents in tackling the daunting task of assimilating massive amounts of information. RadCases second edition primes and expands on concepts found in the first edition with important variations on prior cases, updated diagnostic and management strategies, and new pathologic entities. Our continuing goal is to combine the popularity and portability of printed books with the adaptability, exceptional quality, and interactive features of an electronic case-based format. The new cases will be added to the existing electronic database to enrich the interactive environment of high-quality images that allows residents to arrange study sessions, quickly extract and master information, and prepare for theme-based radiology conferences.

We owe a debt of gratitude to our own residents and to the many radiology trainees who have helped us create, adapt, and improve the format and content of RadCases by weighing in with suggestions for new cases, functions, and formatting. Back by popular demand is the concise, point-by-point presentation of the Essential Facts of each case in an easy-to-read, bulleted format, and a short, critical differential starting with the actual diagnosis. This approach is easy on exhausted eyes and encourages repeated priming of important information during quick reviews, a process we believe is critical to radiology education. New since the prior edition is the addition of a question-and-answer section for each case to reinforce key concepts.

The intent of the printed books is to encourage repeated priming in the use of critical information by providing a portable group of exceptional core cases to master. Unlike the authors of other case-based radiology review books, we removed the guesswork by providing clear annotations and descriptions for all images. In our opinion, there is nothing worse than being unable to locate a subtle finding on a poorly reproduced image even after one knows the final diagnosis.

The electronic cases expand on the printed book and provide a comprehensive review of the entire specialty. Thousands of cases are strategically designed to increase the resident’s knowledge by providing exposure to a spectrum of case examples—from basic to advanced—and by exploring “Aunt Minnies,” unusual diagnoses, and variability within a single diagnosis. The search engine allows the resident to create individualized daily study lists that are not limited by factors such as radiology subsection. For example, tailor today’s study list to cases involving tuberculosis and include cases in every subspecialty and every system of the body. Or study only thoracic cases, including those with links to cardiology, nuclear medicine, and pediatrics. Or study only musculoskeletal cases. The choice is yours.

As enthusiastic partners in this project, we started small and, with the encouragement, talent, and guidance of Timothy Hiscock and William Lamsback at Thieme Publishers, we have further raised the bar in our effort to assist residents in tackling the daunting task of assimilating massive amounts of information. We are passionate about continuing this journey and will continue to expand the series, adapt cases based on direct feedback from residents, and increase the features intended for board review and self-assessment. First and foremost, we thank our medical students, residents, and fellows for allowing us the privilege to participate in their educational journey.

Jonathan M. Lorenz, MD, FSIRHector Ferral, MD

Preface

It is an immense privilege to practice pediatric radiology. Compared to other medical specialists, the radiologist is privileged to peer inside the living human body and contribute to the diagnosis and care of an unusually large number of patients. Compared to other radiologists, pediatric specialists have the opportunity to evaluate all organ systems with every major imaging modality. Nowhere else in radiology is the growth and development of the patient so crucial to care. Above all, pediatric radiology provides an opportunity to contribute to the care of perhaps the most vulnerable and precious patients of all, at all stages from prenatal life through adolescence. It is a blessing to be able to count ourselves among a long line of esteemed colleagues, whose shoulders have provided a perch from which all who study pediatric radiology can see far.

Richard B. Gunderman, MD, PhDLisa R. Delaney, MD

Acknowledgments

Many people have contributed to this work: our colleagues in pediatric radiology at Indiana University, from whom we have learned so much and with whom it remains a privilege to work side by side each day, including Brandon Brown, Matthew Cooper, Donald Corea, Francis Marshalleck, Boaz Karmazyn, Megan Marine, and Matthew Wanner, as well as our recently retired colleague, Mervyn Cohen. Lisa Ferguson and Carlene Webb-Burton provided superb administrative support. RBG also thanks Kelsey Hilaire, Luke Flood, and especially Nathan Gruenhagen for help in preparing many of the cases. Above all, our deepest thanks go to our families for their great patience and support as we labored over this project.

Case 1

■ Clinical Presentation

A 27-day-old boy presents with vomiting that turned bilious on day 2.

■ Imaging Findings

(A) Oblique view from a barium upper gastrointestinal (GI) examination demonstrates dilation of the proximal duodenum that tapers to a beaklike appearance, followed distally by a helical or corkscrew configuration of the distal duodenum (arrow). (B) Frontal view from the same barium upper GI examination demonstrates a corkscrew appearance of the distal duodenum. The duodenal–jejunal junction (arrow) is positioned too caudal to the duodenal bulb.

■ Differential Diagnosis

•Midgut volvulus: The key imaging findings of midgut volvulus include an abnormal position of the duodenal–jejunal junction, in which radiographic contrast does not cross completely over to the left side of the spine, and a corkscrew configuration of the distal duodenum.

•Gastroenteritis: Most infants who present with bilious vomiting do not have an anatomic abnormality and instead are suffering from a functional condition such as gastroenteritis or feeding intolerance.

•Congenital duodenal obstruction: Conditions such as duodenal atresia and duodenal webs can be associated with bilious vomiting when the point of obstruction is distal to the ampulla of Vater.

■ Essential Facts

• Midgut volvulus occurs in patients with intestinal malrotation, whose small bowel mesentery has an abnormally short mesenteric root and is therefore prone to twisting or volvulus.

• Midgut volvulus involves twisting of the bowel around the axis of the superior mesenteric artery, which can cause ischemia and infarction of the bowel.

• Many patients with malrotation also have Ladd bands, abnormal adhesion-like fibrous bands that can cause intestinal obstruction independent of volvulus.

• Surgical correction via the Ladd procedure involves untwisting the bowel and fixing it to the peritoneal wall to prevent future volvulus, as well as lysis of Ladd bands.

■ Other Imaging Findings

• Plain radiographs may be normal, particularly if the stomach and proximal duodenum have been decompressed by vomiting or passage of a nasogastric tube.

• Cross-sectional imaging such as abdominal ultrasound or CT may show an abnormal relationship of the superior mesenteric artery and vein, with the vein lying to the left of the artery.

• Cross-sectional imaging may also show a helical or swirling of bowel around the axis of the superior mesenteric artery, best appreciated when scrolling through axial images.

✓ Pearls and ✗ Pitfalls

✓ In cases where the position of the duodenal–jejunal junction is equivocal, the progression of radiographic contrast can be followed through to the cecum, which is in its normal position in the right lower quadrant in only 20% of patients with malrotation.

✗ Note that patients who have undergone the Ladd procedure will still have malrotated bowel, with the small bowel on the right and large bowel on the left.

Case 2

■ Clinical Presentation

A fetus at 21 weeks’ gestational age with abdominal wall defect seen on fetal ultrasound image.

■ Imaging Findings

(A) Sagittal true fast imaging with steady-state precession (TrueFISP) fetal MR image. Part of the liver (thick arrow) and a small amount of bowel (asterisk) are seen outside of the abdominal cavity. There is a curvilinear membrane (curved arrow) covering the defect. The umbilical cord (arrow) inserts on the inferior aspect of the membrane. (B) Sagittal T2 half-Fourier acquisition single-shot turbo spin-echo (HASTE) fetal MR image. The hernia sac (arrow) is better delineated on this image. The umbilical cord insertion onto the sac (curved arrow) again can be seen.

■ Differential Diagnosis

•Fetal omphalocele: A congenital midline abdominal wall defect with abdominal contents herniating into a sac onto which the umbilical cord inserts is consistent with an omphalocele.

•Gastroschisis: These abdominal wall defects are usually to the right of midline and are not covered by a membrane. The umbilical cord inserts normally on the abdominal wall, not on the defect.

•Physiologic gut herniation: Loops of bowel should never be seen outside of the abdominal cavity beyond 13 weeks of gestational age. In addition, physiologic herniation should only contain bowel loops, not liver.

■ Essential Facts

• Associated anomalies are frequent and include cardiac, genitourinary, skeletal, and central nervous system. In addition, omphaloceles are associated with multiple syndromes including trisomies, Turner syndrome, Klinefelter syndrome, and others.

• Detection of associated anomalies is crucial for prognosis. The mortality rate is very high with any associated defect and severely high with associated chromosomal or cardiovascular anomalies. An isolated omphalocele has a much better prognosis.

■ Other Imaging Findings

• Almost always initially discovered on fetal ultrasound image demonstrating multiple bowel loops herniating into a membrane-covered defect.

• Umbilical cord insertion is always on the membrane covering the herniation.

• Allantoic cyst in the umbilical cord is common.

✓ Pearls and ✗ Pitfalls

✓ Associated anomalies appear to be more frequent the earlier the omphalocele occurs in gestation and in smaller omphaloceles that contain only bowel.

✗ If the omphalocele ruptures, the membrane covering the herniated contents will be difficult to visualize and can be difficult to distinguish from gastroschisis.

Case 3

■ Clinical Presentation

A fetus at 38 weeks’ gestational age with concern for chest mass on fetal ultrasound image.

■ Imaging Findings

(A) Coronal half-Fourier acquisition single-shot turbo spin-echo (HASTE) fetal MR image. There are multiple loops of small bowel (asterisk), colon (arrow), and spleen (dot) in the left chest cavity causing mass effect on the normal right lung (curved arrow). (B) Coronal HASTE fetal MR image. The liver (asterisk) and stomach (arrow) are not herniated into the chest cavity. The heart (curved arrow) is displaced to the right.

■ Differential Diagnosis

•Congenital diaphragmatic hernia (CDH): Abdominal contents in the hemithorax is consistent with CDH.

•Congenital pulmonary airway malformations (CPAM): Although this also appears as fluid-filled cysts in the hemithorax, the cysts are not typically tubular like bowel and they are more uniform in appearance than a CDH that contains bowel and organs.

•Bronchopulmonary sequestration (BPS): These are typically well-defined and triangular in shape and homogeneously high T2 signal. Often, a feeding vessel from the aorta can be identified.

■ Essential Facts

• CDH can occur on either the left or right side. It is rarely bilateral.

• When CDH occurs on the right, liver is always herniated along with variable amounts of bowel and stomach.

• Associated anomalies include BPS, cardiac anomalies, aneuploidy, and multiple syndromes.

■ Other Imaging Findings

• Fetal MRI can be used to calculate a lung to head ratio and to measure fetal lung volumes, both of which help to predict outcomes based on lung hypoplasia.

• The cardiomediastinum shifts away from the hernia.

• Bowel loops are absent in the abdomen.

• On fetal ultrasonography, a CDH often appears as a cystic lung mass. In addition, if the stomach and small bowel are at the same transverse level as the heart on the four-chamber view on fetal ultrasound image, this confirms CDH.

• On fetal ultrasound image of a right CDH, color Doppler imaging may demonstrate leftward bowing of the umbilical segment of the portal vein, and portal branches to the lateral segment of the left lobe may course toward or above the diaphragm.

✓ Pearls and ✗ Pitfalls

✓ Most common on the left side.

✓ The degree of pulmonary hypoplasia, mediastinal shift, early diagnosis, and location of the liver (above or below the hemidiaphragm) all affect prognosis.

✓ MRI can reliably distinguish CPAM, BPS, and CDH, which is crucial for perinatal planning.

✗ No single parameter has been found to strongly correlate with survival or need for extracorporeal membrane oxygenation; however, there is a composite prognostic index used at some centers that may more strongly correlate with outcomes.

Case 4

■ Clinical Presentation

A fetus at 28 weeks’ gestational age with hydrocephalus on fetal ultrasound image.

■ Imaging Findings

(A) Sagittal true fast imaging with steady-state precession (TrueFISP) fetal MR image. Marked hydrocephalus (asterisk) is seen with a small posterior fossa (black arrow). There is herniation of the cerebellar tonsils to the level of the cervical spine (white arrow). From approximately T12 to L4, there is absence of the posterior elements and a myelomeningocele sac (curved arrow).

■ Differential Diagnosis

•Chiari III malformation: A small posterior fossa with descent of the brainstem and cerebellum as well as a myelomeningocele is characteristic of Chiari II malformation.

•Chiari I malformation: This does have caudal descent of the cerebellar tonsils but would not have the associated myelomeningocele. These are often asymptomatic until adulthood.

•Chiari II malformation: This has features of Chiari II, but instead of a lumbar myelomeningocele, there is an occipital or high cervical encephalocele.

■ Essential Facts

• Myelomeningocele is defined as the protrusion of neural elements and meninges through a bony spinal defect. It is the most common form of neural tube defect.

• Chiari II malformation is also known as Arnold–Chiari malformation.

• Causes varying degrees of paralysis, bladder and bowel morbidity, and developmental delay.

• Studies have shown that the higher the level and larger the size of the myelomeningocele as well as an absence in membranous covering are associated with increasingly adverse outcomes.

• Early causes of mortality include brainstem dysfunction, ventriculitis, and shunt-related complications. Renal disease is the main cause of mortality later in life.

■ Other Imaging Findings

• Other findings of Chiari II in the brain can include colpocephaly, inferior pointing of the lateral ventricles, fenestration of the falx cerebri with interdigitation of the gyri across midline, enlargement of the massa intermedia, tectal beaking, and subependymal gray matter heterotopia.

• In the axial plane of the spine, the open spinal dysraphism is identified as absence of the overlying muscle and skin.

• Can be associated with club foot, scoliosis, and Lückenschädel skull.

✓ Pearls and ✗ Pitfalls

✓ When there is a myelomeningocele, there is almost always a small posterior fossa and associated findings, and vice versa.

✓ On prenatal ultrasound image, the lemon sign (concavity of the frontal bones) and the banana cerebellar sign (cerebellum tightly wrapped around the brainstem) can be seen.

✗ The lemon sign on prenatal ultrasound image usually is not seen past 24 weeks’ gestational age.

✗ Myelomeningoceles are associated with Chiari II malformations, but meningoceles are not.

Case 5

■ Clinical Presentation

A 10-year-old boy with cystic fibrosis exacerbation.

■ Imaging Findings

(A) Axial CT image of the chest. There is a tubular soft tissue density extending from the right hilum to the pleura (asterisk). (B) Coronal maximum intensity projection image of the chest. Seen again is the tubular opacity extending from the hilum in the right upper lobe (asterisk). In addition, along the inferior edge of the tubular density, there is tree-in-bud density (arrow).

■ Differential Diagnosis

•Allergic bronchopulmonary aspergillosis (ABPA): Saccular bronchiectasis filled with soft tissue density is consistent with a bronchocele. This combined with the history of cystic fibrosis should raise concern of ABPA.

•Bronchial atresia: Bronchoceles are also seen in bronchial atresia. They are usually surrounded by an area of hyperinflation and decreased vascular markings. In addition, this is not associated with cystic fibrosis.

•Endobronchial lesion/foreign body: Again, this could be associated with air-trapping but is not associated with cystic fibrosis.

■ Essential Facts

• ABPA is a hypersensitivity reaction to Aspergillus that occurs in patients with cystic fibrosis or asthma.

•Aspergillus grows in the airway, leading to bronchospasm and bronchial wall edema and causing bronchial wall damage and bronchiectasis.

• Segmental and subsegmental bronchi become filled with mucus, Aspergillus, and eosinophils.

■ Other Imaging Findings

• On chest X-ray, findings of asthma or cystic fibrosis may be present with superimposed fleeting opacities representing eosinophilic pneumonia.

• Mucoid impaction in dilated bronchi may appear masslike or branching and may cause atelectasis.

• CT findings include fleeting opacities, bronchiectasis, and bronchoceles (mucus-filled dilated bronchi). Findings are predominantly upper lobe in distribution.

• Bronchoceles can be described as finger-in-glove; tram-line shadows; bandlike (toothpaste) shadows; and sometimes “V,” inverted “V,” or “Y” shaped.

• If left untreated, ABPA can lead to extensive bronchiectasis and fibrosis.

✓ Pearls and ✗ Pitfalls

✓ In ~30% of patients, the mucus becomes calcified and has high density on CT images (the mucus plug is visually denser than the paraspinal muscles).

✓ Many patients cough up thick mucus plugs that may be orange in color.

✗Aspergillus can cause many different findings in the lungs depending on the patient’s comorbidities and amount of fungus present.

Case 6

■ Clinical Presentation

An 8-year-old with abdominal pain after a fall.

■ Imaging Findings

(A) Transverse abdominal ultrasound image demonstrates an elongated hypoechoic fluid collection behind the left lobe of the liver (arrow). (B) Coronal postcontrast CT scan demonstrates a hypodense fluid collection in the expected location of the distal duodenum (arrows).

■ Differential Diagnosis

•Duodenal hematoma: The shape of the fluid collection follows the course of the distal duodenum, and its slight hyperintensity compared to the small amount of adjacent ascites suggests a hematoma.

•Pancreatic pseudocyst: Pancreatic pseudocysts in the lesser sac can assume an elongated shape, but it would be unusual for one to parallel the course of the distal duodenum so closely.

•Duodenal duplication cyst: Such cysts are typically found along the wall of the duodenum, but they do not typically have such an elongated shape and their walls should demonstrate the “bowel signature,” which is not seen here.

■ Essential Facts

• Associated with lap belt ecchymosis, handlebar injury, and child abuse.

• Patients commonly present with abdominal pain and vomiting.

• Most duodenal hematomas resolve spontaneously without surgery.

■ Other Imaging Findings

• Traumatic duodenal hematomas are often associated with other injuries involving such structures as the pancreas and liver.

• Large hematomas such as this can be associated with duodenal obstruction.

• Over days, the density and echogenicity of a duodenal hematoma will tend to decrease.

✓ Pearls and ✗ Pitfalls

✓ In some cases of duodenal obstruction, it may be necessary to place a nasojejunal tube to permit feeding.

✗ It is important not to overlook findings of duodenal perforation, such as extraluminal gas, extravasated contrast, and discontinuities in the duodenal wall.

Case 7

■ Clinical Presentation

A 13-year-old girl with a chest mass.

■ Imaging Findings

(A) Axial postcontrast CT image of the chest. There is a heterogeneous, well-marginated, round mass (asterisk) adjacent to the pulmonary trunk (arrow). It is of mixed density but likely contains low-density areas consistent with fat (curved arrow).

■ Differential Diagnosis

•Teratoma: An anterior mediastinal mass that contains fat is consistent with a teratoma.

•Lymphoma: Although lymphoma is more common, lymphoma should not contain fat.

•Thymoma: Thymoma only comprises 1 to 2% of mediastinal masses in children and would not contain fat. Thymomas typically enhance and can have areas of necrosis.

■ Essential Facts

• Teratomas contain all three germ cell layers and thus can contain fat, fluid, and calcifications.

• The most common germ cell tumor in the mediastinum is a teratoma.

• Germ cell tumor is the second most common mediastinal mass after lymphoma.

■ Other Imaging Findings

• Calcification occurs in ~25% of teratomas and can be curvilinear, central, or peripheral.

✓ Pearls and ✗ Pitfalls

✓ In order to diagnose a primary malignant mediastinal germ cell neoplasm, a primary gonadal tumor as a source of mediastinal metastases has to be excluded.

✓ The more solid components a tumor has, the more likely it is to be benign.

✗ Although teratomas can have fat, fluid, and calcification, all of those characteristics may not be visible on imaging.

✗ Multiple tumors in the mediastinum can contain fat, including mediastinal lipoma, mediastinal lipomatosis, thymolipoma, and liposarcoma.

Case 8

■ Clinical Presentation

A 3-day-old infant with prenatal hydronephrosis.

■ Imaging Findings

(A) Oblique view from a voiding cystourethrogram. There is an abrupt change in caliber (arrow) of the penile urethra with upstream dilation. There is mild trabeculation of the bladder wall (curved arrow) with right vesicoureteral reflux to the dilated, tortuous ureter (asterisk) and distended right renal collecting system (dot).

■ Differential Diagnosis

•Anterior urethral valve (AUV): The abrupt change in caliber of the penile urethra is consistent with AUV. Furthermore, the trabeculation of the bladder and severe vesicoureteral reflux are due to the significant lower urinary tract obstruction.

•Posterior urethral valve (PUV): The urethral dilation in PUVs is in the posterior (prostatic) urethra.

•Prune belly (Eagle–Barrett) syndrome: Prune belly syndrome shares some similarities of AUVs including a dilated urethra, trabeculation of the bladder, tortuosity of the ureters, and vesicoureteral reflux. Other important findings in prune belly include bulging flanks due to absence of the abdominal wall musculature and cryptorchidism. Other genitourinary findings of prune belly can include scaphoid urethra, urachal diverticulum, and opacification of the utricle.

■ Essential Facts

• AUVs may be found anywhere in the anterior urethra.

• PUVs are 15 to 30 times more common than AUVs.

■ Other Imaging Findings

• The valve itself may appear as a linear filling defect along the ventral wall.

• Alternatively, the valve itself may not be seen and is only indicated by a dilated urethra ending in a smooth bulge or an abrupt change in the caliber of the dilated urethra.

• Vesicoureteral reflux occurs in one third of cases.

• A trabeculated bladder with diverticula and a urethral diverticulum may also be seen.

• AUVs may be associated with urethral diverticula. Some consider them as separate entities, whereas others consider them part of the same entity.

✓ Pearls and ✗ Pitfalls

✓ Valves of Guerin are AUVs occurring in the most distal aspect of the urethra, the fossa navicularis.

✗ Patients with AUV have extremely variable presentations depending upon the degree of obstruction and the patient’s age. Symptoms can range from urinary incontinence and retention with a weak urinary stream to infection, urosepsis, and renal failure.

Case 9

■ Clinical Presentation

A 4-year-old boy with unsteady gait.

■ Imaging Findings

(A) Sagittal T2-weighted MR image of the spine. There is a large, ovoid, expansile intramedullary mass (asterisk) within the lower thoracic spinal cord from approximately T9 to T11. It has predominately low T2 signal but has some central increased T2 signal. Superior to this mass from approximately T6 to T8, there is an expansile cystic lesion (dot) with a rim of low T2 signal. (B) Sagittal T1 fat-saturated postcontrast image of the spine. There is contrast enhancement of the solid mass (asterisk) from T9 to T11 but not of the cystic mass (dot).

■ Differential Diagnosis

•Spinal cord astrocytoma: An enhancing, infiltrating mass that expands the spinal cord is consistent with an astrocytoma.

•Spinal cord ependymoma: These are uncommon in children but can appear similar to astrocytomas of the spinal cord. Ependymomas more often contain hemorrhage and are usually more well-defined than astrocytomas.

•Syringohydromyelia: This is a nonenhancing cystlike cavity in the spinal cord that is usually associated with a malformation such as Chiari I, spinal dysraphism, Dandy–Walker, or diastematomyelia.

■ Essential Facts

• Astrocytoma is the most common spinal cord neoplasm in children.

• Subarachnoid dissemination may occur.

■ Other Imaging Findings

• Mild scoliosis, widened intrapedicular distance, and bone erosion may be seen on plain film.

• On CT image, cord expansion can often be identified. The tumor itself may be difficult to resolve; however, it will usually enhance.

• Intratumoral and peritumoral cysts and surrounding edema are common.

• Astrocytomas may appear largely extramedullary.

• Involvement of the entire spinal cord (holocord involvement) is common in children.

✓ Pearls and ✗ Pitfalls

✓ Astrocytomas arise in the cord parenchyma, whereas ependymomas arise in the central canal.

✗ In one series, 20 to 30% of astrocytomas did not enhance.

Case 10

■ Clinical Presentation

A 15-year-old girl with a lump in her neck.

■ Imaging Findings

(A) Axial postcontrast CT image of the neck. Just deep to the right sternocleidomastoid muscle (asterisk), posterolateral to the right submandibular gland (arrow), and lateral to the right internal carotid artery and jugular vein (bracket) is a well-circumscribed fluid density lesion (dot) with a smooth, thin rim of peripheral enhancement.

■ Differential Diagnosis

•Second branchial cleft cyst (type II): This is the classic location of a branchial cleft cyst.

•Thyroglossal duct cyst: Typically, these are midline or slightly off midline.

•Suppurative lymph node: Although a suppurative lymph node could be low density with a thin rim of enhancement, this is fairly large for a lymph node and there are no other reactive lymph nodes in the area.