Ebook Diagnostic imaging of infants and children: Part 2

(BQ) Part 2 book Diagnostic imaging of infants and children presents the following contents: Congenital abnormalities of the brain, intracranial infections, autoimmune disorders of the brain, intracranial neoplasms and masses, neoplasms and masses of the spine, trauma and surgery of the spine,...

Diagnostic Imaging of Infants and Children

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Diagnostic Imaging of Infants and Children

Pediatric Diagnostic Imaging, SC PDI Pediatric Teleradiology Milwaukee, Wisconsin Director, Pediatric Imaging Northwestern Lake Forest Hospital

Lake Forest, Illinois Associate Clinical Professor of Radiology and Pediatrics

Medical College of Wisconsin Milwaukee, Wisconsin

edical New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto

� M cGrow · H/1/ CompanieS

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To Annie,

my loving wife and best friend

To my sons, Jack, Sam, and Joe,

who have taught me much more than I will ever teach them

And to Jack Sty,

who one day said to me, "Bob, let's write another book "

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Contents

Foreword ix 16 Intracranial Infections ···597

Preface xi 17 Autoimmune Disorders of the Brain 625

Acknowledgments xiii 18 Metabolic and Destructive Disorders of the Brain 641

VOLUME I 19 Intracranial Neoplasms and Masses 683

PART 1 THE THORAX 1 20 Intracranial Vascular Abnormalities 797

1 Developmental Abnormalities 21 Head Trauma 847

of the Lungs and Diaphragm 3

2 Neonatal Lung Disease 45

3 Pulmonary Infection 75

PART 4 THE SPINE 887

22 Developmental Abnormalities of the Spine 889

4 Chronic Lung Disease, Genetic Abnormalities, and Systemic Disease 139 23 Infection, Inflammation, and Degenerative Disorders of the Spine 957

5 Pulmonary Neoplasms and Masses 179 24 Neoplasms and Masses of the Spine 977

6 Pulmonary Trauma, Surgery, and Toxins 191 25 Trauma and Surgery of the Spine 1007

7 The Mediastinum 219

8 The Chest Wall 251 VOLUME II 9 The Breast 267 PART 5 THE HEAD AND NECK 1043

26 The Skull and Face 1045

PART 2 THE CARDIOVASCULAR 27 The Orbit 1 091 SYSTEM 277

10 Acquired Diseases of the Heart and Pericardium 279

11 Congenital Heart Disease 315

12 Anomalies of the Great Vessels 403

13 The Vascular System 433

28 The Paranasal Sinuses 1137

29 The Nose, Nasal Cavity, and N asopharynx 1153

30 The Neck, Pharynx, and Trachea 1173

31 The Salivary Glands 1249

32 The Thyroid and Parathyroid Glands 1261

PART 3 THE BRAIN 485 33 The Temporal Bone and Ear 1293

14 Congenital Abnormalities of the Brain 487

15 Hydrocephalus 575

vii

viii Contents

SYSTEM 1 323 and Stones 1813

34 The Esophagus 1325 51 Urinary System Trauma, 35 The Stomach 1357 Surgery, and Therapy 1827

36 The Smalllntestine 1379 52 Renal Vascular Abnormalities 1841

37 The Colon 1447 53 The Female Genital System 1855

38 The Omentum, Mesentery, 54 The Male Genital System 1887

and Peritoneal Cavity 1495 55 Genital Abnormalities that 39 The Anterior Abdominal Wall 1503 Affect Both Genders 1925

40 Abdominal Trauma and Other lntraabdominal Emergencies 1511 PART 11 THE ADRENAL CiLANDS 1 931 56 The Adrenal Glands 1933

PART 7 THE HEPATOBILIARY SYSTEM 1521 PART 12 THE MUSCULOSKELETAL 41 The Hepatobiliary System 1523 SYSTEM 1965

57 Skeletal Dysplasias 1967

PART 8 THE PANCREAS 1607 58 Dysostoses and Developmental 42 The Pancreas 1609 Deformities 2029

59 Metabolic Bone Diseases 2073

PART 9 THE SPLEEN 1629 Go Systemic Arthritis 2113

43 The Spleen 1631

61 Hematological and PART 10 THE GENITOURINARY SYSTEM 1 653 Ischemic Bone Disease 2123

62 Musculoskeletal Infections 2141

44 Developmental Abnormalities 63 Musculoskeletal Tumors 2161

of the Urinary System 1655 64 Nonneoplastic Abnormalities 45 Renal Cysts 1715 of the Extremity Soft Tissues 2237

46 Diseases of the Renal Parenchyma 1741 65 Musculoskeletal Trauma 2259

47 Urinary System lnfection 1759

48 Vesicoureteral Reflux 1777 Index /-1

49 Neoplasms and Masses

Foreword

Diagnostic Imaging of Infants and Children by Robert Wells

is a must-have text that I am sure you will keep as a con­

stant friend It is a one-of-a-kind book, written in a style

that is concise and informative Kudos to Dr Wells for the

superlative work

This richly illustrated reference covers the gamut of

pediatric diseases and injuries Extensive integration of

clinical considerations and review of disease pathogenesis

help to make sense of imaging patterns and provide the

radiologist with tools to establish a confident diagnosis

Readers of various backgrounds will find this text use­

ful Radiologists can pull it off the shelf for a quick review

of the imaging findings and differential diagnosis of a con­

dition, with additional material available for those desiring

a more in-depth review of the clinical presentation and

pathophysiology For clinicians, this text is a resource for reviewing the advantages and disadvantages of various imaging approaches and for understanding the signifi­ cance of imaging findings The easy-to-read style and the clear correlation of radiologic findings with disease patho­ physiology and clinical features make it an excellent choice for medical students, residents, and fellows

This text is a terrific source of information across the entire spectrum of pediatric radiology, and I strongly rec­ ommend this book to anyone interested in the subject

Richard Towbin, MD Radiologist-in-Chief Phoenix Children's Hospital

Phoenix, Arizona

ix

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Preface

Diagnostic Imaging of Infants and Children is designed to be

an efficient reference source for the practicing radiologist,

a learning tool for radiology residents and fellows, and a

cross-specialty resource for all medical providers who care

for children Technologists in all imaging modalities will

also find it useful The text is comprehensive, but concise

Up-to-date descriptions of the clinical features, pathogen­

esis, and pathology of diseases provide a solid background

for understanding diagnostic imaging principles The con­

tent encompasses essentially all pediatric conditions for

which diagnostic imaging is clinically important

The basic organization of the text is by organ system

and disease category For each condition, the reader is pre­

sented with a brief overview of current information about

the pathogenesis, epidemiology, and clinical presentation

When appropriate, discussion of the disease pathology is

correlated with the findings on diagnostic imaging stud­

ies The imaging features with each pertinent imaging

modality are reviewed sequentially Imbedded "Pathology­

Radiology" tables provide a quick reference for the key

findings

Because the approach to the individual patient does not always fit with a disease category system, there are sup­ plemental features in the text that provide the reader with additional tools Clinical Presentations sections interject discussions of key symptom-based considerations about the differential diagnosis and imaging procedure selec­ tion In addition, differential diagnosis tables are included where appropriate

Radiologists, pediatricians, pediatric specialists, and other health care professionals who care for children face the ongoing and evermore complex challenge of choosing the most accurate, least invasive, and most cost-effective diagnostic imaging techniques for the individual patient The balanced approach of this text provides the reader with tools to make informed decisions in everyday practice The information in Diagnostic Imaging of Infants and Children is the result of an exhaustive review of the current medical literature, blended with the practical knowledge accumulated from nearly 30 years of practice as a pediatric radiologist My sincere wish is for my fellow radiologists and clinical colleagues to find this a useful resource as they strive to provide high-quality care to children

xi

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Acknowledgments

This book would not exist without the encouragement,

guidance, and support of Dr Jack Sty He has been a men­

tor, colleague, and friend throughout my career His enthu­

siasm for excellence is infectious My love for teaching and

writing has grown under his influence

My partner, Dr Brian Lundeen, has been instrumen­

tal in helping to maintain our clinical practice as I have

balanced my clinical duties with this time-consuming

project He has also contributed many of the figures in the

text and assisted with proofing figure legends Dr Smita

Bailey, now at Phoenix Children's Hospital, has also pro­

vided key images

The physician assistants, nurses, and technologists

at our outpatient radiology center, Pediatric Diagnos­

tic Imaging, have contributed in various ways, includ­

ing manuscript proofing and acquisition of illustrative

images Special thanks to Darci Grochowski for her assis­

tance with the musculoskeletal chapter

Several dedicated people assisted with photography,

image organization, clinical correlation, and bibliographic

research They include Jessica Mainus-Sohns, Scott Byers,

Kevin Cohen, and Monica Godat Thanks as well to the fi le

room staff and technologists at the Children's Hospital of

Wisconsin The potentially chaotic process of preparing thousands of images for use in the book ran with preci­ sion under the guidance of my dedicated and energetic administrative secretary, Sue Armson Sue passed too early, but her spirit is part of this book

I wish to acknowledge Dr Jeff Rosengarten and the other members of the radiology department at Northwest­ ern Lake Forest Hospital High-quality images from this institution are scattered throughout the text Also, thanks

to Dr Darin Brannan and the staff at The Children's Cen­ ter in Bethany, Oklahoma

The editors and production staff at McGraw-Hill have been supportive and professional Special thanks to Michael Weitz and Peter Boyle

Finally, the special contribution of my family needs

to be recognized My three sons, Jack, Sam, and Joe, have tolerated a father who needed to devote large blocks of time to this project Only my oldest can remember a time when dad was not working on "the book." They have been unwavering in their support and encouragement My dear wife, Annie, is the unnamed coauthor of this book She has provided encouragement and advice Her uncondi­ tional support made this book possible

xiii

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Diagnostic Imaging of Infants and Children

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CH A PTE R 1 Developmental Abnormalities

of the Lungs and Diaphragm

EMBRYOLOCY OF TH E LU NCS

AND PULMONARY VESSELS 3

DEVELOPM ENTAL ABNORMALITI ES OF TH E LU NCS 4

Pulmonary Agenesis and Aplasia 4

Pulmonary Hypoplasia 6

Bronchial Atresia 8

Bronchopul monary Sequestration 9

Extralobar Sequestration 1 o Intralobar Sequestration 11

Congenital Cystic Adenomatoid M alformation 11

Pulmonary Bronchogenic Cyst 19

Accessory Bronchus .. .. 20

Tracheal Bronchus 20

Esophageal Bronchus 21

Bridging Bronchus 21

Accessory Cardiac Bronchus 21

Congenital Bronchial Stenosis 22

Congenital Lobar Emphysema . 22

Horseshoe Lung 24

Lung Hernias 25

ANOMALI ES OF PULMONARY VESSELS 25

I nterruption ofthe Main Pulmonary Artery 25

EMBRYOLOGY OF THE LUNGS AND PULMONARY VESSELS Fetal lung development can be categorized into the embry­ onic, pseudoglandular, canalicular, and saccular phases.1 Embryonic development begins at 24 to 26 days gesta­ tion when a diverticulum arises from the ventral wall of the foregut Over the next 2 days, the right and left lung Anomalous Origi n of the Left Pulmonary Artery 26

Systemic Arterial Supply 26

Anomalous Pulmonary Venous Con nection 26

Anomalous Si ngle Pulmonary Vein 27

Pulmonary Arteriovenous M alformation 28

Pulmonary Varix 30

COM BI N ED ANOMALI ES OF LU NC AND PULMONARY VESSELS 30

Hypogenetic Lung Syndrome 30

DEVELOPM ENTAL LYM PHATIC DISORDERS 32

DEVELOPM ENTAL ABNORMALITI ES OF TH E DIAPHRACM . .. .. .. .. . ... 33

Congenital Diaphragmatic Hernia 33

Eventration 38

Congenital Paralysis of the Hemidiaphragm ..... 3 9 Hepatic-Pulmonary Fusion 39

REFERENCES 39

buds arise from this diverticulum The developing air­ ways become separated from the esophageal portion

of the foregut by ingrowths of adjacent mesoderm that form the tracheoesophageal septum The lung buds elon­ gate into primary lung sacs, and the 5 secondary bronchi develop as outgrowths of the primary bronchi This com­ pletes the embryonic period, at approximately the end of the fifth week

3

4 Part 1 The Thorax

The pseudoglandular phase predominantly consists of

development of the bronchial tree During this phase, the

airways are blind tubules lined with columnar or cuboidal

epithelium The pseudoglandular phase occurs between the

fifth and 16th weeks of gestation Nearly all of the conducting

airways are present by the end of the pseudo glandular phase

The canalicular phase represents the early stage of

development of transitional airways There is decrease

in mesenchymal tissue within the developing lungs, and

newly formed capillaries and air spaces approximate one

another The canalicular phase occurs between the qth

week and the 25th to 28th weeks

The saccular (or alveolar) phase relates to develop­

ment of the alveoli Defined acinar morphology is present

by the 28th week of gestation During the final weeks of

fetal development, there is prolific development of alveoli

Alveolar development continues in postrlatal life to approx­

imately the age of 8 years

Tracheal cartilage development predominantly occurs

during the pseudoglandular and canalicular periods Initial

cartilage development occurs during the seventh to eighth

weeks of gestation Bronchial cartilage development occurs

in a centrifugal direction

Anomalies of the lung related to abnormal broncho­

pulmonary �ung bud) development include agenesis, bron­

chial atresia, tracheal atresia, some instances of congenital

lobar emphysema, congenital cystic adenomatoid malfor­

mation, pulmonary bronchogenic cyst, tracheal bronchus,

and accessory cardiac bronchus The pathogenesis of bron­

chogenic cysts apparently involves abnormal epithelial bud­

ding caused by local defects in the mesenchymal substrate 2

The faulty development that results in cystic adenomatoid

malformation occurs later in gestation, and is character­

ized by disordered development of the bronchioles and fail­

ure of differentiation of the epithelium into a mature form

This may be related to faulty signaling between the bron­

chioles and peribronchial mesenchyme during the period

of active bronchial development, which occurs between the

fifth and eighth weeks.3 The developmental mechanism

of pulmonary sequestration involves both abnormal bron­

chial budding (supernumerary budding from the foregut,

or pinching off from the developing bronchial tree) and

failure of normal mesenchymal maturation (persistent sys­

temic arterial supply).4·5 Congenital lobar emphysema can

be caused by any developmental abnormality that results in

lobar air trapping, such as a focal anomaly of airway carti­

lage, intrinsic or extrinsic bronchial obstruction, or abnor­

mal supporting stroma of the alveolar wall.6.7

A spectrum of anomalies results from arrested devel­

opment of lung; this is termed the agenesis-hypoplasia

is an important determining factor in the nature of the

resultant anomaly The patterns include agenesis (absence

of bronchus and lung), aplasia (absence of lung, but pre­

served bronchus), and hypoplasia (rudimentary bron­

chus and lung) The agenesis-hypoplasia complex most

often involves an entire lung or lobe (hypogenetic lung

syndrome) Developmental arrest occasionally occurs at the segmental level Segmental bronchial agenesis most often involves the right upper lobe.8.9

The pulmonary arteries develop from the sixth aortic arch The proximal part of the sixth aortic arch becomes the proximal segments of the right and left pulmonary arter­ ies On the left, the connection with the arch is maintained

as the ductus arteriosus Pulmonary arterial development parallels that of the airways during fetal development Postrlatal development results in increase in peripheral ves­ sel branching commensurate with alveolar development until approximately 8 years of age Anomalies of pulmonary artery development include agenesis, hypoplasia, anoma­ lous systemic connection, and arteriovenous malformation During the embryonic phase of fetal development, pul­ monary venous blood drains from the splanchnic plexus into the primordium of the systemic venous system Pulmonary venous development begins with caudal and cranial outpouchings of the sinoatrial regions of the heart These extend toward the lung buds The caudal outpouch­ ing regresses The cranial portion develops as the common pulmonary vein Eventually, the common pulmonary vein incorporates into the left atrial wall Residual splanchnic pulmonary connections regress This leaves 4 independent pulmonary veins entering the left atrium Potential pulmo­ nary venous anomalies include pulmonary varix, systemic connection, and agenesis

Congenital lung malformations comprise a heteroge­ neous and overlapping group of anomalies (Table 1-1) The terminology applied to these lesions is often imprecise There is overlap of the embryological, pathological, clinical, and radiological features of these various lesions A num­ ber of classification schemes have been proposed in an attempt to provide order to the sometimes confusing array

of anomalies Many investigators consider lung anomalies

to represent a spectrum of pulmonary and vascular mal­ development.10 Bush proposed simplified nomenclature based on the gross anatomy and imaging appearance The

5 major categories in this system consist of a congenitally enlarged hyperlucent lobe, congenital thoracic malforma­ tions, a congenitally small lung, absent lung, absent tra­ chea, and absent bronchus." Langston has developed a classification system based on the pathologic features and presumed embryogenesis Table 1-1 is adapted from this system Langston emphasizes the importance of develop­ mental airway obstruction in the pathogenesis of multiple seemingly unrelated lung malformationsP

DEVELOPMENTAL ABNORMALITIES OFTHE LUNCS

Pul monary Agenesis and Aplasia Pulmonary agenesis is the complete absence of lung paren­ chyma, vessels, and bronchial structures in a lung, a lobe,

or (rarely) both lungs Pulmonary aplasia represents the

Chapter 1 Developm ental Abnormal ities of the Lungs a n d D i a p h ragm 5

Table 1-1 Congenital Lung Malformations

Absent or small lung Pulmonary hypoplasia

Pulmonary agenesis - - -

Pulmonary aplasia

· · - - _

B ronchopul monary malformation

Pulmonary hyperplasia and

related lesions

Congenital lobar overinflation

Bronchogenic cyst

I solated bronchial atresia

B ronchial atresia with systemic vascu lar connection (intralobar sequestration)

Anomalous bronchial connection to the gastroi ntestinal tract Cystic adenomatoid malformation, large cyst type

-Cystic adenomatoid malformation, small cyst type

Extralobar sequestration Laryngeal atresia

-Hypogenetic lung syndrome Anomalous pul monary venous connection

I nterru ption of main pulmonary artery

M iscellaneous cystic lesions

Pulmonary arteriovenous malformation Lym phatic cysts

Enteric cysts

S i m ple parenchymal cysts

same constellation of findings except that a rudimentary

bronchus is present Pulmonary agenesis and aplasia

result from a developmental abnormality at approximately

4 weeks of gestational age The anomaly usually involves

an entire lung The left upper lobe is the most common site

of lobar agenesis/aplasia The contralateral lung typically

has compensatory enlargement, but is otherwise normal

Morbidity and mortality are greater in those patients with

right lung agenesis than in those with involvement of the

left lung, presumably as a result of more pronounced medi­

astinal shift and concomitant torsion of the great vessels

and major airways

More than 50% of children with pulmonary agenesis

or aplasia have coexistent congenital anomalies of the

cardiovascular, gastrointestinal, skeletal, or genitourinary

systems Patent ductus arteriosus and patent foramen

ovale are the most common cardiovascular anomalies in

these children The associated skeletal anomalies of the

limbs and spine tend to be ipsilateral to the lung abnor­

mality Ipsilateral radial ray defects and hemifacial micro­

somia can occur in association with pulmonary agenesis

Severe cardiac anomalies are more common in patients with agenesis of the right lung than with agenesis of the left lung.'3·'4

Symptomatic children with agenesis of a lung often have anatomic distortion of the airway and vascular com­

pression In some patients, there is intrinsic airway ste­

nosis Symptomatic newborns exhibit manifestations of respiratory distress: tachypnea, cyanosis, and impaired gas exchange

Imaging studies demonstrate shift of normal lung to fill the void created by agenesis or aplasia There is marked mediastinal shift and the contralateral lung bulges across

lung herniation varies between patients If the left lung

is absent, the right cardiomediastinal border sometimes produces a sharp perpendicular line adjacent to the left margin of the sternum as viewed on a frontal radiograph

With agenesis of the right lung, the left cardiomediastinal border is shifted to the right of the sternum and the entire cardiac silhouette is contiguous with that of the liver (Figu re 1-2) The ribs are crowded together on the side of

6 Part 1 The Thorax

A

8

A, B Anteroposterior and lateral radiographs show a small left

hemithorax and leftward shift of the mediastinal structures The

left lung is absent There is marked leftward displacement of

hyperexpanded right lung

the absent lung Bronchography and bronchoscopy dem­

onstrate absence of the main bronchus in patients with

agenesis Cross-sectional imaging with MR or helical CT

shows absence of lung parenchyma, bronchial structures,

and pulmonary and bronchial vessels on the affected

side These studies are also valuable for documenting

Figure 1-2 Pulmonary agenesis

There is no aerated right lung on this anteroposterior chest radiograph of a newborn infant The hyperinflated left lung herniates across the midline (arrows) There is rightward shift

of the trachea The outlines of the heart are not visible; the soft­ tissue density of the cardiac structures in the right hemithorax

is contiguous with that of the liver There are right-sided rib deformities and spinal segmentation anomalies

secondary effects on the airway and mediastinal vessels The imaging appearance of pulmonary aplasia is identical

to that of agenesis except that a rudimentary bronchus is present.'5·'6

The radiographic findings of lobar agenesis/aplasia are subtle Most often, the ipsilateral lung is small and the remaining lobes are hyperinfl.ated There may be an abnor· mal density in the region of the involved lobe that mim­ ics atelectasis Agenesis of the right middle lobe and right upper lobe or of the left upper lobe results in a retroster· nal density that parallels the anterior chest wall on lateral radiographs At times, the radiographic appearance of lobar agenesis mimics that of lobar collapse If the standard radiographic findings are inconclusive, computed tomog­ raphy is diagnostic MR can be helpful to demonstrate sec­ ondary airway abnormalities, and to define the mediastinal vascular anatomy.'5·16

Pul monary Hypoplasia

The definition of pulmonary hypoplasia is deficient or incomplete development of the lung, such that there is decreased size of the lung and a diminished number

of functioning pulmonary units (i.e., cells, airways, and alveoli) Both lungs are involved in most patients with pulmonary hypoplasia Unilateral or lobar forms also occur, usually associated with anomalies of the ipsilateral

Chapter 1 Develo pmental Abnormalities of the L u n gs a n d D i a p h ragm 7

A

A An anteroposterior chest radiograph of a newborn with

respiratory distress and abdominal distention shows small­

volume lungs, elevation of the diaphragm, and mild cardiomegaly

pulmonary artery and pulmonary veins Bilateral pulmo­

nary hypoplasia typically causes severe, often fatal, neona­

tal respiratory distress.'7·18

Pulmonary hypoplasia occurs as a primary lesion in

10% to 15% of cases The more common secondary form is

associated with one or more other conditions that directly

or indirectly interfere with lung development, usually by

compromising the thoracic space available for lung growth

Intrathoracic lesions are most common; these include

congenital diaphragmatic hernia, extralobar sequestra­

tion, agenesis of the diaphragm, and a large fetal pleural

effusion or chylothorax Asphyxiating thoracic dystrophy

(Jeune syndrome) is an example of a thoracic cage anomaly

that compromises fetal lung development Others include

short-rib polydactyly syndromes, metatrophic dysplasia,

Ellis-van Creveld syndrome, achondrogenesis, and severe

forms of osteogenesis imperfecta Extrathoracic causes of

pulmonary hypoplasia include oligohydramnios (e.g., renal

agenesis, severe urinary tract obstruction) and abdomi­

nal distention (e.g., ascites, polycystic kidney disease)

Diminished pulmonary vascular perfusion as a result of

a cardiac or vascular anomaly can also lead to pulmonary

hypoplasia."'

The clinical presentation of pulmonary hypoplasia var­

ies according to the severity of the anomaly Most often,

there are manifestations of respiratory distress in the

B

B An abdominal radiograph shows large flank masses caused

by polycystic kidney disease, resulting in abdominal distention, displacement of bowel, and elevation of the diaphragm

newborn, with cyanosis, tachypnea, hypoxia, hypercapnia, and acidosis With severe bilateral involvement, there may

be rapid progression to death from severe hypoxemia The small lungs are difficult to ventilate, and complications of mechanical ventilation are common; these include pulmo­ nary interstitial emphysema, pneumothorax, pneumome­ diastinum, and pneumopericardium Pneumothorax can also develop spontaneously in these infants

The radiographic diagnosis of bilateral pulmonary hypoplasia is sometimes difficult Lung aeration can ini­ tially appear normal on chest radiographs The small size

of the lungs may not be appreciated until serial radiographs show that the appearance is persistent The thoracic cage

is usually small and the diaphragm is elevated (Figure 1 -3) Unilateral pulmonary hypoplasia appears radio­ graphically as a small, but well aerated, lung The ipsilat­ eral pulmonary artery is small or absent Occasionally, an anomalous draining pulmonary vein is visible (e.g., scimi­ tar syndrome) The hypoplastic lung is oligemic, and blood flow to the contralateral lung may be increased The medi­ astinum is deviated toward the side of the hypoplasia; this

is accentuated during inspiration (Figure 1-4) The radio­ graphic differential diagnosis includes hypogenetic lung syndrome, Swyer-James McLeod syndrome, and urlliateral absence of the pulmonary artery Occasionally, there is cys­ tic distention of the hypoplastic lung (possibly as a result of

8 Part 1 The Thorax

A

Figure 1-4 Pulmonary hypoplasia

Anteroposterior and lateral chest radiographs of an asymptomatic

4-year-old child show diminished size of the right lung, with

a developmental defect at the bronchial-alveolar junction),

resulting in an appearance that overlaps that of congenital

cystic adenomatoid malformation

The early prenatal detection of clinically significant

pulmonary hypoplasia is helpful for parental counsel­

ing and planning for optimal perinatal management

Techniques for assessing the fetus with suspected pulmo­

nary hypoplasia include various measurements based on

sonography and MRI Sonographic measurements that

can be useful include the ratio of fetal lung area to thoracic

area, the ratio of thoracic circumference to abdominal cir­

cumference, and the ratio of lung area to thoracic area

MR allows estimation of the fetal lung volume, which can

be compared to the expected values for the gestational age

or evaluated as a ratio of lung volume to estimated body

weight.'9-2'

Potter syndrome refers to a constellation of findings that

occur with bilateral renal agenesis and other conditions

that cause severely diminished urine excretion in utero

The findings include severe pulmonary hypoplasia, oligo­

hydramnios, and dysmorphic features The bilateral pul­

monary hypoplasia in these infants usually results in death

soon after birth Potter syndrome occurs in approximately 1

in 3000 livebirths _The newborn with Potter syndrome has

characteristic features that include hypertelorism, epican­

thic folds, low-set ears, a flattened nose, micrognathia, and

limb anomalies; the facial appearance in these children is

termed Potter facies 22

B

obscuration of the right cardiomediastinal border, rightward shill

of the mediastinal structures, and lack of appropriate anterior extension of the right lung (arrows) on the lateral view

Many clinicians also use the term Potter syndrome

to refer to similar, but not necessarily lethal, features of infants who are the products of pregnancies in which there is severe oligohydramnios from causes other than bilateral renal agenesis A more proper term in this situation is Potter phenotype These mimicking condi­ tions account for approximately 8o% of newborns with manifestations of the Potter phenotype These abnor­ malities include cystic renal dysplasia, severe obstructive uropathy, autosomal recessive polycystic kidney disease, renal hypoplasia, medullary dysplasia, and Denys-Drash syndrome 23-25

Bronchial Atresia Bronchial atresia is a focal obliteration of a proximal seg­ mental or subsegmental bronchus The pathogenesis of bronchial atresia is unknown, but apparently involves an insult to a formed bronchus rather than a primary devel­ opmental failure One potential mechanism is an interrup­ tion of the arterial supply of a developing fetal bronchus, with subsequent ischemia and scarring or discontinuity between the cells at the tip of the bronchial bud and the more proximal aspect of the developing bronchus Despite the presence of an atretic bronchial segment, the distal branches can develop normally Typically, the abnormality involves segmental bronchi at or near their origins; how­ ever, lobar or subsegmental bronchi can also be involved

Chapter 1 Developmental Abnormal ities of the L u n gs and D i a p h ragm 9

The most common site is the apical posterior bronchus of

the left upper lobe Other potential sites include the seg­

mental bronchi of the right upper lobe, right middle lobe,

and right lower lobe.'2·26

At the parahilar margin of the affected portion of the

lung, a segment of the bronchus immediately distal to

the atresia is dilated and filled with mucous; this is the

bronchocele (mucocele) that is a characteristic feature

of bronchial atresia The cystic, blindly terminating,

mucus-filled bronchocele does not connect to the main

bronchial tree The more distal bronchi are filled with

mucous, but otherwise are relatively normal The alve­

oli in the lobe or segment distal to the atretic bronchus

are ventilated by collateral pathways, and this portion

of the lung becomes hyperinflated and noncollapsible

Occasionally, there is associated microcystic parenchy­

mal maldevelopment

Most patients with bronchial atresia are asymptom­

atic Recurrent lung infections can occur Other potential

clinical findings include dyspnea and manifestations of

bronchial asthma Pectus excavatum is sometimes associ­

ated with bronchial atresia, possibly because of costoster­

nal retraction during the efforts to overcome the airway

obstruction caused by encroachment on normal lung tis­

sue by the hyperinflated segments Spontaneous pneumo­

thorax occasionally occurs as a complication of bronchial

atresia.27

Chest radiographs of children with bronchial atresia

show a hyperinflated lobe or segment, and a round or lob­

ulated parahilar mass (the bronchocele) (Figure 1 -5) The

parahilar mass may appear solid or cystic, and it sometimes

has a branching character The mass represents dilated

Figure 1-5 Bronchial atresia

mucous-filled bronchi distal to the obstruction The appear­

sign The portion of lung distal to the mass is hyperinflated The involved lung is also oligemic, a result of intrapulmo­ nary vascular compression and hypoxic vasoconstriction Expiratory CT is particularly useful for demonstrating the hyperinflated portion of involved lung, as well as the central branching bronchocele that has attenuation characteristics

of soft tissue or fluid With MRI, the bronchocele appears

as a branching structure radiating from the hilum, with high signal intensity on both T1-weighted and T2-weighted images Lp8-32

On prenatal sonography, the portion of lung involved with bronchial atresia appears enlarged and hyperechoic Enlarged branching central bronchi may be visible There is sometimes a cystic character The pathologic anatomy can also be demonstrated with fetal MR In the neonate, bronchial atresia appears as a radiographically opaque segment or lobe, due to retention of fetal alveolar fl.uid.33-35

The radiographic differential diagnosis of bronchial atresia includes allergic bronchopulmonary aspergillosis, cystic bronchiectasis, bronchogenic cyst, and intrapulmo­ nary sequestration (bronchial atresia with systemic vascu­ lar connection) Any acquired lesion that causes proximal airway obstruction and focal air trapping can have a radio­ graphic appearance that is similar to that of congenital bronchial atresia; examples include foreign body, tumor, and inflammatory stricture CT usually allows accurate exclusion of a hilar mass in these children, and aids in the distinction between mucoid impaction and nodular lesions Contrast-enhanced spiral CT allows exclusion

of an anomalous vascular component, as occurs with sequestration

Bronchopul monary Sequestration Bronchopulmonary sequestration is a mass composed of lung tissue that receives its blood supply from an anoma­ lous systemic artery and does not communicate with the bronchial tree via anatomically normal bronchial struc­ tures Bronchopulmonary sequestration, like hypogenetic lung syndrome, is a combined anomaly of tracheobronchial development and pulmonary vascular development There are 2 main types: intralobar and extralobar (Table 1 -2) An intralobar sequestration is within the visceral pleura The arterial supply is by one or more anomalous systemic arter­ ies, and drainage is usually via the pulmonary veins An extralobar sequestration is contained in a pleural envelope separate from that of the normal lung, is supplied by one

or more anomalous systemic arteries, and can have various pathways of venous drainage.36.37

The typical treatment for bronchopulmonary seques­ trations is surgical resection The intralobar type usually requires a formal lobectomy.s Because some extralobar sequestrations regress or disappear spontaneously, nonoperative management is appropriate for selected

10 Part 1 The Thorax

of l ntralobar and Extralobar Types

Prenataljinfancy 8o% male - - - ·-· - · - · - · - - - -

left, 40% right go% left

Arterial su pply Systemic Systemic

Com mon Rare

asymptomatic patients.38 Transcatheter embolization is an

additional nonsurgical therapeutic option that frequently

results in complete disappearance of the lesion.39-41

Extralobar Sequestration

An extralobar sequestration results from aberrantly located

mesenchyme that develops apart from the normal lung

The pathogenesis likely involves abnormal budding of

the primitive foregut (i.e , an anomalous or supemumer·

ary lung bud) Therefore, this is a type of noncommuni·

eating bronchopulmonary foregut malformation, as is

bronchogenic cyst Although there is no communication

with the tracheobronchial tree, bronchial atresia is not the

primary embryonic event in this anomaly Persistence of

primitive splanchnic arteries that supply the foregut dur·

ing fetal development leads to systemic arterial supply of

the sequestration The mass contains dilated bronchioles,

alveoli and subpleural lymphatic vessels The original con·

nection with the foregut disappears or regresses to form

a fibrous pedicle Occasionally, a patent communication

Table 1-3 Echogenic Lu ng Masses on Prenatal Sonography48

(esophageal bronchus) with the gastrointestinal tract per· sists; the lesion may then be termed a bronchopulmonary foregut malformation H2

Extralobar sequestration occurs with a 4=1 male-to· female ratio More than half of children with extralobar sequestration have an associated anomaly, such as con· genital diaphragmatic hernia, diaphragmatic eventration, diaphragmatic paralysis, cystic adenomatoid malforma· tion, bronchogenic cyst, foregut duplication, pericardia! defect, vertebral anomalies, ectopic pancreas, or pectus excavatum Extralobar sequestration is supradiaphragmatic

in 90% of patients; usually located between the left lower lobe and the left hemidiaphragm Other potential locations include the mediastinum, within the diaphragm, and, rarely, below the diaphragm The arterial supply is from the aorta or a primary branch of the aorta; 15% are supplied

by an artery that arises below the diaphragm One-fifth of these lesions are fed by multiple arteries The venous drain· age is most often via a systemic vein, typically in the azygos

or hemiazygos systems; portal or pulmonary venous con· nections can also occur.5A3

Extralobar sequestration is typically asymptomatic Most are detected on routine prenatal sonography or on

a chest radiograph obtained of an infant or child for an unrelated indication A large lesion can cause respira· tory distress in the neonate The radiographic appearance

is easily confused with that of pneumonic consolidation, and the diagnosis is sometimes first established when CT

is performed to evaluate a "recurrent" or "nonclearing" pneumonia in an older infant or child In other patients, the lesion is detected during the diagnostic workup of an associated thoracic or cardiac anomaly Rarely, the lesion produces a symptomatic left-to-right shunt Congenital ten· sion hydrothorax caused by torsion of a sequestration has been reported.44·45

Extralobar sequestration can be detected prenatally with sonography or MR as a solid well-defined triangular mass in the lower aspect of the thorax, usually on the left The complex character of the lesion results in a hyperechoic appearance on sonography The differential diagnosis includes various other congenital lung lesions (Table 1·3) With MR the lesion produces greater signal intensity than

Congenital cystic adenomatoid malformation

B ronchopul monary sequestration

B ronchogenic cyst

Congenital diaphragmatic hernia

Cystic and solid; someti mes spontaneous resol ution Solid, ± small cysts; sometimes spontaneous resol ution - · · - - - · - · - - - · - - - -

U n i locu lar cyst; two-thi rds in middle or posterior med iastin u m, one-thi rd in lung

I ntrathoracic extension of bowel or viscera

M ediasti nal mass

Chapter 1 Developm ental Abnormal ities of the L u n gs a n d D i a p h ragm 1 1 lung o n T2-weighted images Cystic areas are sometimes

visible If a systemic feeding artery can be visualized, this

finding is helpful in confirming the diagnosis In 6% to

10% of cases, a pleural effusion accompanies the lesion;

this may be a result of dilated subpleural lymphatics or

torsion around the connecting vasculature Rarely, a large

pleural effusion leads to compression of the vena cava and

heart, causing fetal hydrops; this can be treated with in

utero drainage Partial or complete spontaneous regres­

sion of extralobar sequestrations is common during fetal

life; approximately three-quarters of these lesions undergo

relative decrease in size in utero The fetus with suspected

sequestration should be carefully evaluated for potential

accompanying anomalies.34·46·47

In the neonate, the sonographic appearance of an

extralobar sequestration is that of an echogenic mass, usu­

ally located adjacent to the diaphragm The degree of sono­

graphic heterogeneity of the lesion varies between patients

Rarely, small hyperechoic foci are present because of collat­

eral air drift An additional rare pattern is that of multiple,

small, fluid-filled cysts Sonography of the affected neonate

sometimes allows visualization of an anomalous supply­

ing artery arising from the aorta An attempt should also

be made to demonstrate the pattern of venous drainage

Enlargement of the azygos and hemiazygos vessels can

occur in these infants

Extralobar Pu lmonary Sequestration

Dysplastic lung

No bronchial tree

com m u nication

Soft-tissue mass Airless

Persistent s planchnic arteries Systemic arterial su pply

The pathologic anatomy of extralobar sequestration is

optimally demonstrated with helical CT or MRI The hall­

mark feature is at least one large systemic artery supplying

the lung "mass." With CT, the lesion is typically homoge­

neous; occasionally, there are internal cysts The margins

are relatively well defined, and may be lobulated Adjacent

atelectatic lung sometimes obscures the borders, however

No air is present within the mass unless there is superim­

posed infection or a connection with the gastrointestinal

system.42·49

In those unusual instances of sequestration in which

there is a patent communication with the gastrointestinal

system, air bronchograms may be visible within the lesion

CT shows the communication as an air-filled tubular struc­

ture extending toward the esophagus An upper GI contrast

study usually allows definitive demonstration of an esopha­

geal bronchus.5°

Intralobar Sequestration

Intralobar sequestration is a form of bronchial atresia in which there is systemic arterial supply to the involved por­ tion of the lung Langston terms this as bronchial atresia

intralobar sequestration is from the thoracic or abdomi­ nal segments of the aorta in 75% of instances, and other thoracic systemic vessels in 25% Potential supplying arter­ ies include the celiac, splenic, intercostal, subclavian, and coronary arteries Venous drainage is often through the pulmonary veins As with isolated bronchial atresia, paren­ chymal maldevelopment similar to the small cyst type of cystic adenomatoid malformation can occur with intralobar sequestration.'2·5'-54

As compared to the extralobar type, intralobar seques­ tration usually presents later in childhood Most patients have manifestations of recurrent or persistent pulmonary infection Infection is much more common with intralobar sequestration than with the extralobar type Hemoptysis may occur Rarely, there are signs of congestive failure because of shunting through the lesion Hemothorax caused by infarction of an intralobar sequestration has been reported

An intralobar sequestration is usually visualized on standard chest radiographs as a soft-tissue density lung mass with smooth or lobulated margins It is most often

Other potential imaging findings include bronchiectasis, atelectasis, mediastinal shift, and prominence of the ipsi­ lateral pulmonary hilum In some patients, suggestive findings of a sequestration are recurrent lower-lobe pneu­ monias or the presence of a rounded consolidation that does not clear completely with antibiotic therapy.5'·55 The computed tomographic appearance of intralo­ bar sequestration is variable Potential findings include a homogeneous soft-tissue mass, a cystic lesion containing air or fluid, focal emphysema with surrounding solid tis­

Calcifications are occasionally present The anomalous sys­ temic vascular supply and the pathway of venous drainage are demonstrable with helical CT, MR angiography, or cath­

drainage of an intralobar sequestration is via pulmonary veins rather than systemic veins; however, this finding alone does not provide accurate distinction from an extralo­ bar sequestration.5'·54-57

Congen ital Cystic Adenomatoid Malformation

Congenital cystic adenomatoid malformation (congeni­

opmental lesion composed of cystic and solid dysplastic pulmonary tissue The lesion has hamartomatous char­ acteristics pathologically It consists of immature lung tissue, with proliferation of bronchioles that form cysts

12 Part 1 The Thorax

A

8

Figure 1-6 I ntralobar sequestration

A, B Posteroanterior and lateral chest radiographs show

a homogeneous soft tissue-density mass in the posterior

basal portion of the left lung Air bronchograms are lacking

The patient had no symptoms of pneumonia, and follow-up

radiographs (not shown) demonstrated persistence of the opacity

rather than normal alveoli The lesion usually contains

both cystic and solid tissue The pathogenesis likely

involves a maturation defect in lung embryogenesis, with

failure of the pulmonary mesenchyme to induce normal

bronchoalveolar differentiation during the fifth through

seventh weeks of gestation Discordant development of

the vascular and mesenchymal components of the devel­

oping lung leads to an abnormal proliferation of these

structures Immunohistochemical analysis of the cellular

components of congenital cystic adenomatoid malfor­ mation suggests that there is an arrest or disruption of normal branching morphogenesis, which causes an over­ growth of respiratory epithelium The solid adenomatoid form apparently is embryologically distinct from the more common cystic variety.3·58.s9

Congenital cystic adenomatoid malformation accounts for approximately 25% of all congenital lung abnormali­ ties The prevalence is slightly higher in males than in females There is equal frequency of occurrence in both lungs There is a slight predilection for location in the upper lobes; it is uncommon in the right middle lobe Congenital cystic adenomatoid malformation can occur in association with a pulmonary sequestration; this is sometimes termed

a hybrid lesion.6o-62 Congenital cystic adenomatoid mal­ formation can also be associated with congenital bronchial atresia.63

Congenital cystic adenomatoid malformation is classi­ cally divided into 3 types, based on the gross and micro­ scopic features) Although there is substantial overlap in the clinical and pathological features of cystic adenomatoid malformation in individual patients, there is utility in con­ sidering the 3 basic types as separate entities Type I �arge cyst type) is most common, accounting for approximately 70% of cases This lesion contains one or more cysts that are at least 2 em in diameter The cysts communicate with adjacent airways, and have some pathologic features of dilated bronchi There are often adjacent smaller cysts and solid components Type II (small cyst type) cystic adeno­ matoid malformation contains numerous cysts between 0.5 and 2 em diameter The cysts are lined by cuboidal to columnar epithelium, and histologically resemble dilated terminal and respiratory bronchioles This lesion some­ times occurs as a secondary phenomenon because of a localized embryonic airway obstruction; that is, bronchial atresia The rare type III cystic adenomatoid malformation (solid type) is a grossly solid-appearing lesion that contains tiny cysts (<o.s em) on histologic examination This adeno­ matoid or solid form of congenital pulmonary airway mal­ formation may represent localized pulmonary hyperplasia

in response to fetal airway obstruction.3·12·64 The most common clinical presentation of congeni­ tal cystic adenomatoid malformation is acute progressive respiratory distress, which develops shortly after birth The infant may have cyanosis, grunting, retractions, and tachy­ pnea Rarely, there is sudden onset of symptoms caused

by a pneumothorax Physical examination demonstrates diminished breath sounds at the site of the lesion, hyper­ resonance, and shifted cardiac sounds If the lesion is small, the clinical presentation may occur beyond the peri­ natal period, with respiratory distress, failure to thrive, or recurrent pneumonia Fetal lung compression by a large cystic adenomatoid malformation can cause symptomatic pulmonary hypoplasia Nonimmune fetal hydrops can also occur with a large lesion, as a result of impaired cardiac contractility and impaired venous return to the heart; this finding indicates a grave prognosis 65

Chapter 1 Develo pmental Abnormal ities of the L u n gs a n d D i a p h ragm 1 3

c

In some patients, the clinical presentation of congeni­

tal cystic adenomatoid malformation does not occur until

adulthood or late childhood These patients often present

with recurrent pneumonia localized to the involved lobe.66

Diagnosis of the underlying congenital malformation may

be difficult in these patients, as inflammation, abscess

formation, and fibrosis can result in the formation of

epithelial-lined pulmonary cysts that are radiographically

and pathologically similar to the cysts of congenital cys­

tic adenomatoid malformation.64 In addition to recurrent

infection, late-onset congenital cystic adenomatoid malfor­

mation may come to clinical attention because of a pneu­

mothorax or as an incidental finding on an imaging study

performed for another indication 67

The macrocystic forms of cystic adenomatoid malfor­

mation are generally considered to carry a more favorable

prognosis than the rnicrocystic variety, although the medi­

cal literature does not uniformly support this concept

Approximately 50% of infants with the type I I malformation

B

A There is a somewhat heterogeneous left lower-lobe mass

are irregular and lobulated B Angiography shows multiple anomalous feeding vessels (arrow) arising from the aorta

C A venous phase image shows drainage of the lesion into a pulmonary vein (arrow)

have other anomalies, some of which adversely affect the prognosis These associated anomalies include renal agen­ esis, extralobar sequestration, and sirenomelia Associated anomalies occur in only approximately 10% of infants with type I congenital cystic adenomatoid malformation Type

I I I congenital cystic adenomatoid malformation is usually

a large lesion that produces marked respiratory distress Cardiovascular compromise is a potential complication of mediastinal displacement Any type of cystic adenomatoid malformation that occupies a substantial portion of the chest cavity during fetal development can cause compres­ sion and hypoplasia of the ipsilateral lung

On prenatal sonography, type I congenital cystic adeno­ matoid malformation appears as a simple or complex fluid­ filled mass that contains one or more large cysts The type

II lesion consists of multiple small cysts with interspersed echogenic parenchyma The type III lesion is a homoge­ neous echogenic mass.48,54 Occasionally, differentiation between congenital cystic adenomatoid malformation

14 Part 1 The Thorax

A

c

and congenital diaphragmatic hernia is difficult on pre­

natal ultrasound; MRI may be helpful in this situation

(Figure 1 -9 ).68 In addition, the prenatal imaging appear­

ance of the type III adenomatoid variant often is identical

to other solid pulmonary lesions, such as sequestration

Approximately three-fourths of fetuses with cystic

adenomatoid malformation survive Some authors report

lower survival rates with type III lesions, but other stud­

ies have not confirmed this pattern A poor outcome is

likely if prenatal sonography shows nonirnmune hydrops

Polyhydramnios, caused by esophageal compression by

the lung mass or increased fluid production from the

abnormal lung tissue, is associated with a guarded prog­

nosis.48 Spontaneous in utero regression of congenital

B

Figure 1 8 I ntralobar sequestration

A A coronal contrast-enhanced CT image of a 2-year-old male with a persistent left lower-lobe opacity

on chest radiographs demonstrates a solid mass in the inferior aspect of the left hemithorax There are multiple large vessels within the lesion

B A reformatted CT angiography image shows a

The enlarged draining veins extend from the superior aspect of the mass C An axial image at the level of the left atrium shows the enlarged draining pulmonary vein (arrow)

cystic adenomatoid malformation occurs in a substantial minority of cases Regression is demonstrated on prena­ tal sonography as temporal decrease in size of the lesion relative to the remainder of the fetus, or (rarely) complete disappearance.69·7° This is most common with a type II lesion However, CT imaging of the newborn with prenatal sonographic evidence of complete spontaneous resolution

of a mass frequently detects residual abnormalities, even if chest radiographs are normal.7'

The radiographic findings of infants with congenital cystic adenomatoid malformation are variable The most characteristic appearance is that of multiple rounded, air­

the newborn, the cysts often contain fluid, resulting in the

Chapter 1 Developm ental Abnormal ities of the L u n gs a n d D i a p h ragm 1 5

A coronal fetal M R image (fast imaging with steady-state

precession [FISP]) demonstrates multiple large cysts replacing

the left lung (arrow) There is rightward displacement of the

mediastinal structures, including the heart (H) (L, Liver.) The

left hernidiaphragm is intact Polyhydramnios, subcutaneous

edema, and fetal ascites indicate significant fetal compromise

radiographic appearance of a solid intrapulmonary mass

As fluid clears and is replaced by air in the macrocystic

forms of this lesion, the cystic character becomes evident

radiographically (Figu re 1-11} The air-filled cysts may pro­

gressively enlarge with time and compress adjacent medi­

astinal structures and normal lung tissue (Figure 1-12}

Pneumothorax can occur Because the type III lesion con­

tains cysts that are too small to be resolved radiographi­

cally, the imaging appearance is that of a solid mass that

displaces adjacent structures A large congenital cystic

adenomatoid malformation, regardless of type, produces

mediastinal shift, displacement of the hernidiaphragm,

and atelectasis or hypoplasia in adjacent lung At the other

extreme, a small congenital cystic adenomatoid malforma­

tion can be radiographically occu1t.64,7'

Postnatal sonography can be useful if radiographs

show a solid-appearing intrathoracic mass in the newborn

The cystic nature of the type I and type II lesions can be

effectively demonstrated by this technique Typically, there

is a complex internal appearance that includes multiple

cysts, internal septations, and solid elements The type

III lesion has an echogenic, solid-appearing character on

sonography.72

A

B

Anteroposterior and lateral chest radiographs o f a 4-week-old infant with respiratory distress show large air-filled cysts in the upper aspect of the left chest cavity, with adjacent atelectasis

Congenital Cystic Adenomatoid Malformation

Proliferation of im m ature l u ng tissue Pul monary mass

B ronchiolar cysts Ai r-fil led cysts

Com m u nication with bronchial tree

CT is the optimal technique for demonstrating the pathologic anatomy in many children with congenital cystic adenomatoid malformation A type I lesion has one or more large air-filled cysts, usually surrounded

1 6 Part 1 The Thorax

A

B

A There is faint homogeneous opacity (arrow) in the medial

superior aspect of the left hemithorax on this radiograph

obtained at day 1 of life B Followup CT obtained 4 weeks later

demonstrates two large air-filled cysts that cause rightward

displacement of the mediastinal structures

by smaller cysts and a variable amount of soft tissue

(Figure 1-1 3) The soft-tissue attenuation areas correspond

histologically to glandular tissue or bronchiolar struc­

tures Occasionally, areas surrounding the macroscopic

cysts have attenuation values intermediate between those

of air and soft tissue (lower than normal lung) ; this tis­

sue corresponds histologically to microscopic cysts and

thin-walled structures resembling small bronchioles

If there is superimposed infection, cystic adenomatoid

malformation appears as a complex lesion on CT, with

combined cystic and solid components, air-fluid levels,

and ill-defined margins (Figures 1 -1 4 and 1 - 1 5) A Type II

Figure 1-12 Congenital cystic adenomatoid malformation type I

There are multiple large air-filled cysts (arrows) in the right lung

of this 6-day-old infant There is leftward shift of the mediastinal structures

lesion has a heterogeneous appearance on CT, with small variably-sized cysts, often with intermixed soft tissue (Figure 1 - 1 6) As on standard radiographs, a type I I I con­ genital cystic adenomatoid malformation appears as a solid pulmonary mass on CT (Figu re 1-1 7) 54,73.74

The imaging diagnosis of congenital cystic adenoma­ toid malformation is not always straightforward, and there are important considerations in the differential diagnosis

An associated lesion, such as pulmonary sequestration, may complicate the radiographic, pathologic, and surgi­ cal evaluation The multiple air-filled cysts can mimic the appearance of intrathoracic intestine herniated through a congenital diaphragmatic defect Differentiation is aided

by noting a normal abdominal gas pattern with the for­ mer, and diminished bowel gas in the presence of a hernia Occasionally, congenital cystic adenomatoid malformation has a similar appearance as congenital lobar emphysema

on standard radiographs; the cystic nature of the lesion is usually demonstrable on CT A newborn with a fluid-filled solitary type I congenital cystic adenomatoid malforma­ tion may have radiographic and CT findings that do not allow differentiation from a bronchogenic cyst In older children, acquired cystic lesions of the lung are included

in the differential diagnosis; these include lung abscess and pneumatocele (infection, trauma, hydrocarbon aspira­ tion) Type III cystic adenomatoid malformation is part of the differential diagnosis of a solid intrathoracic mass in a

Chapter 1 Developmental Abnormal ities of the L u n gs and D i a p h ragm 1 7

An unenhanced cr image of a 6-month-old infant shows

multiple air-filled cysts in the right lung There is mild mass

effect on adjacent structures

A

Figure 1-1 5 I nfected type I cystic adenomatoid malformation

A An upright chest radiograph of a 3-year-old child with fever

and cough shows an air-fluid level in a large cavity in the right

Figure 1-14 I nfected congenital cystic adenomatoid malformation

CT of a child with clinical manifestations of pneumonia shows

a complex cystic and solid right-lung mass There is an air-fluid level in a large cyst in the posterior aspect of the lesion

B

lung B Contrast-enhanced CT confirms the presence of a unilocular cyst There is associated pleural fluid

1 8 Part 1 The Thorax

A

Figure 1-1 6 Congenital cystic adenomatoid malformation type I I

A An anteroposterior chest radiograph o f a 12-hour-old newborn

with a history of a prenatally diagnosed cystic right lung lesion

shows ill-defined opacities at the right lung base B Followup CT

at 1 month of age shows replacement of the right lower lobe with

multiple air-filled cysts of varying sizes

A

A , B Sagittal and coronal contrast-enhanced C T images o f an

asymptomatic to-month-old child with a history of a prenatally

detected right lung mass show a solid wedge-shaped lesion

(arrows) at the right lung base Arterial supply and venous

B

B drainage are via pulmonary vessels The lesion appears solid

on CT and undergoes moderate contrast enhancement Histological examination demonstrated dysplastic lung and multiple small cysts

Chapter 1 Developmental Abnormal ities of the L u n gs a n d D i a p h ragm 1 9 neonate; the appearance i s sometimes identical to that o f a

puhnonary sequestration The imaging features of mesen­

chymal cystic hamartoma can be identical to those of cystic

adenomatoid malformation; the pathological features are

also similar

The blood supply of a congenital cystic adenomatoid

malformation is usually derived from the puhnonary artery

However, at least partial supply occurs via an aberrant

artery arising from the aorta in a substantial minority of

patients The imaging findings and pathologic features in

these patients overlap those of bronchopuhnonary seques­

tration Recognition of the anomalous vascular supply is

important for surgical management.54·75

Surgical resection is indicated for patients with a

symptomatic congenital cystic adenomatoid malforma­

tion However, if the neonate is asymptomatic and prena­

tal ultrasound has shown progressive diminution in size

of the lesion, continued observation may be appropriate

to allow for continued spontaneous regression There are

reports, however, of malignancy arising in congenital cys­

tic adenomatoid malformation.76 Therefore, unless there

is complete spontaneous involution of the lesion, surgical

resection is usually indicated, even if there are no symp­

toms.? Intrauterine therapies that have been utilized for

a hydropic fetus with congenital cystic adenomatoid mal­

formation include serial fetal thoracic aspirations, thora­

coarnniotic shunt, and open fetal surgery The selection

criteria for fetal intervention, however, are incompletely

defined.77-79

Pul monary Bronchogenic Cyst

Bronchogenic cyst is a noncommunicating bronchopuhno­

nary foregut malformation The developmental pathophys­

iology of bronchogenic cyst involves abnormal budding

of the developing tracheobronchial tree, with isolation of

a bud from the normal airways Bronchogenic cyst is part

of the spectrum of cystic bronchopuhnonary foregut mal­

formations that also includes foregut cyst, enteric cyst and

neurenteric cyst.2

The lining of a bronchogenic cyst consists of pseu­

dostratified columnar respiratory epithelium The walls

contain cartilage, smooth muscle, and mucous gland tissue

The cyst may contain serous fluid or thick mucoid mate­

rial The lesion does not communicate with the tracheo­

bronchial tree except as a secondary phenomenon because

of instrumentation or infection Approximately two-thirds

of bronchogenic cysts are located within the mediastinum

The most common location is near the carina, in the mid­

dle or posterior mediastinum Those that occur within the

lung are usually solitary, thin-walled, and unilocular The

most common puhnonary sites are the lower lobes Pleural

or diaphragmatic locations can occur Rare sites include the

retroperitoneum and neck Occasionally, a bronchogenic

cyst occurs in association with another congenital puhno­

nary malformation, such as sequestration or congenital

lobar emphysema.8o.8t

A

B

Figure 1-18 Bronchogenic cyst

This 2-week-old infant presented with a history of respiratory distress during feedings A A contrast-enhanced CT image of the upper portion of the chest shows a large oval cyst on the right There is compression of the trachea B An inferior image demonstrates hyperinflation of the right lung caused by airway compression

Bronchogenic cysts are usually asymptomatic and discovered incidentally on imaging studies obtained for another purpose Those patients who are symptom­ atic often have clinical manifestations related to airway compression or, less commonly, secondary infection

(Figu re 1 -1 8) Infection is most common in those broncho­ genic cysts that are located within the lung parenchyma The potential clinical findings include cough, wheezing,

20 Part 1 The Thorax

Figure 1-1 9 I ntrapulmonary bronchogenic cyst

Contrast-enhanced cr of a 4·Week-old child shows a large cyst in

the mid portion of the right lung There is a thin enhancing wall

A small area of calcification is present within the wall {arrow)

stridor, dyspnea, cyanotic spells, and pneumonia Infants

may present with respiratory distress.5·82,83

Standard radiographs most often show a broncho­

genic cyst as a well-defined, solitary mediastinal or hilar

mass Rapid increase in size or accumulation of gas

within the cyst can occur if the lesion becomes infected

Extrinsic compression or deviation of the esophagus is

visible on esophagography in about half of patients with

bronchogenic cyst An intrapulmonary bronchogenic

cyst also appears as a mass; the cyst may be fluid-filled

and homogeneous, or contain an air-fluid level The

inflammatory changes created by secondary infection of

a bronchogenic cyst may lead to a mistaken clinical and

radiographic diagnosis of pneumonia or primary lung

abscess 84,85

On CT, bronchogenic cyst typically appears as a sharply

marginated mediastinal or parahilar mass that has attenu­

ation values of soft tissue or water (Figu re 1 -1 9) The bor­

ders may be smooth or lobulated There is typically little

mass effect associated with a mediastinal bronchogenic

cyst, and the lesion tends to mold around mediastinal

structures rather than displace them Tracheobronchial

narrowing can occur with a large lesion Occasionally, the

cyst contains air or milk of calcium Calcification of the

cyst wall occurs rarely The CT characteristics that indicate

the cystic nature of most of these lesions include inter­

nal homogeneity, enhancement of the wall, fluid attenu­

ation values, and lack of internal enhancement In older

Table 1-4 Fetal Cystic Lesions of the Lung

Pu l monary bronchogenic cyst

Lym phatic malformation

Cystic pleuropu l monary blastoma

patients, CT may show mosaic low attenuation and band­ like linear attenuation in the lung adjacent to an intra­ pulmonary bronchogenic cyst because of emphysema, bronchiolization, or fibrosis 54,86

The M R appearance of a bronchogenic cyst is that of a well-defined mediastinal or pulmonary mass that produces high signal intensity on T2-weighted images The margins are sharp Those cysts that contain clear fluid produce low signal intensity on T1-weighted images; however, the pres­ ence of debris or proteinaceous fluid frequently causes a moderate-to-bright appearance MR is particularly useful

in those instances in which CT does not provide definitive evidence of the cystic nature of the lesion.87

Ultrasound can be useful to document the fluid composition of a suspected bronchogenic cyst The lesion is unilocular, and may have an anechoic or a weakly echogenic appearance, depending on the content Most bronchogenic cysts are not detectable with prena­ tal sonography When this lesion is visible, it usually appears as a unilocular fluid-filled cyst in the middle or posterior mediastinum The differential diagnosis in this situation includes other cystic mediastinal lesions, such

as esophageal duplication cyst and neurenteric cyst The differential diagnosis of a fetal intrapulmonary cyst incu­ des bronchogenic cyst and cystic adenomatoid malforma­ tion (Table 1 -4 ) 54.85,88

The treatment of bronchogenic cyst is surgical resec­ tion Even small asymptomatic lesions may become symptomatic later in childhood or adulthood Malignant degeneration (rhabdomyosarcoma) has been reported within bronchogenic cysts

Accessory Bronch us

Tracheal Bronchus Tracheal bronchus is an anomalous upper lobe bronchus that arises directly from the trachea or from the proxi­ mal aspect of a mainstem bronchus The pathogenesis involves an anomalous tracheal outgrowth that occurs early during embryonic airway development The term

Chapter 1 Developmental Abnormal ities of the L u n gs and D i a p h ragm 21

lobe bronchial anomalies A true tracheal bronchus is a

complete upper-lobe bronchus that arises from the tra­

chea, with no bronchial supply from the normal site in

the mainstem bronchus This anomaly is also termed

cally from the right side of the distal third of the trachea,

within a few centimeters of the carina If there is an upper

lobe bronchus ipsilateral to the tracheal bronchus that is

only missing a segmental branch, the tracheal bronchus

is termed displaced (i.e., a normal branch arising in an

abnormal position) A right-sided displaced bronchus

usually supplies the apical segment, while those located

on the left typically supply the apicoposterior segment

If there is an intact upper-lobe bronchus that branches

normally, the anomalous tracheal bronchus is supernu­

termed a tracheal diverticulum If it supplies aerated lung,

it is termed an apical accessory lung or tracheal lobe All

of the variations of the tracheal bronchus spectrum are

more common on the right 8,14,89

Tracheal bronchus is more common in males and

children with other congenital anomalies Occasionally,

there is concomitant right mainstem bronchus stenosis

Conditions that can occur in association with tracheal

bronchus include bronchiectasis, focal emphysema,

infantile lobar emphysema (usually on the left) , and other

cystic lung malformations Children with tracheal bron­

chus may present with respiratory distress, stridor, cough,

chronic bronchitis, hemoptysis, or recurrent upper lobe

pneumonia The clinical presentation can mimic that of

foreign-body aspiration Treatment recommendations

are based on the severity of symptoms Conservative

management is appropriate for some patients The surgi­

cal option consists of excision of the involved segment

or lobe.9°

Tracheal bronchus is sometimes visible on standard

radiographs However, optimal imaging of the abnormality

is with bronchography or CT In current practice, helical

CT is the imaging modality of choice; there is usually excel­

lent depiction of the pathologic anatomy on reformatted

coronal, three-dimensional, or virtual endoscopic images

(Figure 1- 20) Many of these lesions are discovered inciden­

tally on CT performed for other indications The air-filled

anomalous bronchus arises from an abnormal position in

the trachea or a mainstem bronchus An anomalous fissure

is sometimes visible on CT

Other major bronchial branching anomalies in addi­

tion to tracheal bronchus include accessory cardiac bron­

chus, displaced bronchus, and esophageal bronchus

Asymptomatic anomalous proximal or distal displacement

of segmental or subsegmental bronchi in the same lobe

occurs in up to 10% of the general population Rarely, an

anomalous segmental or subsegmental bronchus origi­

nates from an adjacent lobe, most often in the upper por­

tion of the lung Displacement or fusion of lobar bronchi

can also occur

Figure 1-20 Tracheal bronchus (bronchus suis)

A coronal reformatted CT image of a child with complex congenital heart disease shows a tracheal bronchus (arrow)

supplying the right upper lobe

Esophageal Bronchus The esophageal bronchus arises from the esophagus and

is directed toward either the right or the left lower lobe Esophageal bronchus is a bronchopulmonary foregut malformation, and results from an ectopic supernumer­ ary lung bud The amount of lung tissue supplied by the anomalous bronchus varies considerably between patients If only a small portion of lung is involved, the anomaly may be asymptomatic until infection occurs The diagnosis can usually be established with an esophagram

CT also plays an important role in defining the pathologic anatomy.8

Bridging Bronchus The bridging bronchus is a displaced bronchus that arises from the left main bronchus, crosses through the medias­ tinum, and supplies the right lower lobe (and sometimes the right middle lobe) Most of these patients have one or more associated anomalies Congenital heart disease is common in infants with bridging bronchus; the associated lesions include left-sided obstructive abnormalities and left pulmonary artery sling Respiratory distress and cough are the most common presenting symptoms of bridging bronchus.9'-94

Accessory Cardiac Bronchus

The accessory cardiac bronchus typically arises from the inferior-medial wall of the right main bronchus or bronchus intermedius, and follows a caudal course that

22 Part 1 The Thorax

A

Figure 1-21 Congenital bronchial stenosis

A A coronal reformatted image from a helical cr examination

of a 2-year-old child with a history of stridor since birth and

multiple episodes of pneumonia There is narrowing at

parallels the bronchus intermedius The accessory cardiac

bronchus is supernumerary; that is, it does not supply

normal lung It either supplies a small area of dysplastic

pulmonary parenchyma or ends blindly Accessory cardiac

bronchus is typically asymptomatic Some patients present

with recurrent pneumonia, hemoptysis, or chronic cough

CT may show associated lung parenchymal tissue or a dis­

crete soft-tissue mass representing vascularized bronchial

or vestigial parenchymal tissue The lumen of the anoma­

lous airway is sometimes filled with debris.8.9s.96

Congen ital Bronchial Stenosis

Congenital bronchial stenosis is rare The anomaly can

be unilateral or bilateral Bronchial narrowing as a result

of extrinsic compression is relatively common in chil­

dren with congenital heart disease A common cause of

acquired narrowing of a main bronchus, particularly on

the right, is inflammation caused by frequent suctioning

or prolonged endotracheal intubation Buildup of granu­

lation tissue at the orifice of the bronchus can progress

to symptomatic narrowing An anastomotic stricture is

a frequent cause of bronchial stenosis following lung

transplantation Potential manifestations of clinically sig­

nificant bronchial stenosis on standard radiography are

ipsilateral air trapping and atelectasis Helical CT and vir­ tual bronchoscopy are useful for noninvasive evaluation

of bronchial anatomy in patients with suspected stenosis

(Figure 1- 21).97 Congen ital Lobar Emphysema Congenital lobar emphysema (congenital lobar overinjla­tion; congenital lobar hyperinflation) is characterized by marked overinftation of a single lobe, usually as a conse­ quence of partial obstruction of the lobar bronchus There

is controversy as to whether congenital lobar emphysema

is developmental or acquired; the pathogenesis is likely multifactorial Deficiency of cartilage in the involved lobar bronchus is present in approximately 25% of patients, favor­ ing a developmental etiology However, bronchial mucus plugs or other acquired abnormalities leading to bronchial obstruction may be causative in some patients Congenital cytomegalovirus infection is an occasional causative factor Other reported mechanisms include embryonic dyspla­ sia of the bronchial cartilage, extrinsic compression from

a crossing vessel, a kink in the bronchus, and an intralu­ minal web Consequently, congenital lobar emphysema should be considered a syndrome of lobar air trapping in newborn infants, caused by any one of a number of factors

Chapter 1 Developmental Abnormal ities of the L u n gs and D i a p h ragm 23 that impair bronchial function There is an uncommon

variant of congenital lobar emphysema in which the lobar

overaeration is a result of acinar hyperplasia; this is termed

polyalveolar lobe.7·98-102

Congenital lobar emphysema most commonly involves

the left upper lobe, with approximately half of these lesions

occurring at this site A right middle-lobe location is pres­

ent in approximately 24% of patients and a right upper-lobe

location in 18% Involvement of the lower lobes or multiple

lobes can occur, but is rare The gross pathological appear­

ance of congenital lobar emphysema is that of an enlarged

and overdistended lobe The resected lobe frequently fails

to deflate even when the bronchus is transected Histologic

examination shows distended alveoli and ruptured interal­

veolar septa; fibrosis is lacking The involved lobe other­

wise has the histologic appearance of normal lung With

the polyalveolar lobe variant, the size and shape of alveoli

are normal, but the total alveolar number in the involved

lobe is increased three- to fivefoldY00•101

The clinical presentation of congenital lobar emphy­

sema usually occurs within the first few weeks of life,

often in the immediate perinatal period Approximately

one-third of patients have symptoms soon after birth An

initial presentation beyond 6 months of age is uncom­

mon.85·103 There are rare instances in which children

with congenital lobar emphysema are asymptomatic The

major clinical manifestation of congenital lobar emphy­

sema is respiratory distress Specific findings can include

dyspnea, wheezing, cough, tachypnea, intercostal retrac­

tions, and cyanosis during feeding The symptoms are

sometimes initially mild, and then gradually progress over

a period of a few days to weeks There is a rare fulminant

form, with rapid onset of severe cardiorespiratory com­

promise; this type is often fatal Infants with polyalveolar

lobe usually undergo rapid onset of respiratory distress

during the first day of life; the clinical manifestations are

otherwise indistinguishable from those of "conventional"

congenital lobar emphysema

Physical examination of infants with congenital lobar

emphysema demonstrates an overexpanded hemithorax

that is hyperresonant to percussion The breath sounds in

the area of the abnormal lobe are diminished The cardiac

apex may be shifted toward the contralateral side There is a

slight male predilection Associated anomalies are present

in a minority of patients with congenital lobar emphysema

Approximately 70% of these associated anomalies involve

the cardiovascular system: ventricular septal defect, tetral­

ogy of Fallot, anomalous pulmonary venous connection,

and patent ductus arteriosus.104

The prenatal sonographic features of congenital lobar

emphysema are variable In some instances, the abnor­

mality cannot be identified prenatally In addition, reliable

differentiation form cystic adenomatoid malformation or

pulmonary sequestration is usually not possible until the

postnatal evaluation Two patterns are described on pre­

natal sonography: echogenic and cystic Mediastinal shift

may be present Polyhydramnios can occur.34·105 A single

Figure 1-22 Congenital lobar emphysema

An anteroposterior chest radiograph of a 2-month-old infant with tachypnea shows hyperinflation of the right upper lobe Attenuated lung markings are visible in the overaerated

lobe There is atelectasis in the adjacent portions of the right middle lobe and right lower lobe There is leftward shift of the mediastinal structures The intercostal spaces in the right upper thorax are somewhat expanded

case has been reported in which congenital lobar emphy­ sema had the appearance of an echogenic lung mass on prenatal sonography, but appeared to resolve spontane­ ously prior to delivery.106

The radiographic appearance of congenital lobar emphysema varies with the age of the child at presentation

If imaging is performed soon after birth, the enlarged lobe

is opaque on chest radiographs due to retained fetal lung fiuid.107 The time course for clearance of the fluid ranges from 1 day to 2 weeks A transient reticular pattern may

be present during this period of fl uid clearance Retention

of fetal lung fluid in the abnormal lobe tends to be more prolonged with the polyalveolar variant.98 Subsequently, the characteristic radiographic features of congenital lobar emphysema develop, with hyperlucency and overaeration

of the involved lobe (Figu re 1 -22) The hyperlucent appear­ ance is a result of separation of the pulmonary vascular markings by the hyperinfiated alveoli, as well as local pul­ monary vasoconstriction caused by hypoxia The hyperin­ fiated lobe causes compression of adjacent portions of the lung, mediastinal shift, and localized separation of ribs Occasionally, the hyperinfiated lobe herniates anteriorly across the midline.7·108

CT is useful for evaluating infants with congeni­ tal lobar emphysema if the radiographic findings are equivocal CT is particularly helpful for the differentia­ tion between congenital lobar emphysema and a solitary lung cyst Pulmonary markings are absent in a lung cyst,