Radiographics. 2003;24:e17 Presented by Int. 吳建霆 Dec. 20th, 2005 Congenital Anomalies of the Tracheobronchial Tree, Lung, and Mediastinum Radiographics. 2003;24:e17 Presented by Int. 吳建霆 Dec. 20th, 2005

Outline Tracheobronchial Anomalies Anomalies of the Lung Tracheomalacia Tracheal Stenosis Tracheal Bronchus Bronchial Atresia Bronchogenic Cyst Anomalies of the Lung Pulmonary Underdevelopment Scimitar Syndrome Congenital Cystic Adenomatoid Malformation Congenital Lobar Emphysema Pulmonary Sequestration Esophageal Anomalies Esophageal Atresia and Tracheoesophageal Fistula Esophageal Duplications

Tracheobronchial Anomalies Tracheomalacia Tracheal Stenosis Tracheal Bronchus Bronchial Atresia Bronchogenic Cyst

Tracheomalacia Defined as tracheal wall softening due to an abnormality of the cartilaginous ring and hypotonia of the myoelastic elements Primary tracheomalacia Congenital immaturity of the tracheal cartilage Secondary tracheomalacia Previously normal cartilage undergoes degeneration

Tracheomalacia Symptoms are similar to those of asthma wheeze, cough, stridor, dyspnea, tachypnea, cyanosis, and recurrent respiratory tract infections Associated with other developmental defects such as a vascular ring or tracheoesophageal fistula Congenital diffuse malacia of the airway improves by age 6~12 months

Tracheomalacia Lateral fluoroscopy and esophagography An exaggerated decrease in the caliber of the trachea during expiration

Tracheal Stenosis Characterized by the presence of focal or diffuse complete tracheal cartilage rings, resulting in a fixed tracheal narrowing 50% focal, 30% generalized, and 20% funnel-shaped Symptoms are variable Length of stenosis does not appear to be as critical as degree of stenosis Focal congenital tracheal stenosis consists of a simple local narrowing of the trachea, usually in the lower third Symptoms are variable, depending on the age of the child, the degree of stenosis, and the potential presence of associated anomalies airway resistance is only linearly proportional to length of stenosis, whereas resistance increases fourfold relative to luminal radius decrease

Tracheal Stenosis In isolation or in conjunction with other anomalies The most common is the pulmonary artery sling complex The left pulmonary artery originates from the right pulmonary artery and encircles the right mainstem bronchus and distal trachea

Tracheal Stenosis Frontal and lateral radiographs Combined with ecause of ionizing radiation, CT should be used only in selected cases If necessary, helical CT or electron-beam CT can be useful for evaluating dynamic changes in the airway Magnetic resonance (MR) imaging is valuable for demonstrating the relationship of the airway to adjacent blood vessels without injection of intravascular contrast medium Frontal and lateral radiographs Combined with barium esophagography

Tracheal Bronchus Described as a variety of bronchial anomalies arising in the trachea or main bronchus and directed toward the upper-lobe territory Usually exits the right lateral wall of the trachea less than 2 cm above the major carina Right tracheal bronchus has a prevalence of 0.1%ﾁV2% and left tracheal bronchus a prevalence of 0.3%ﾁV1% in bronchographic and bronchoscopic studies

Tracheal Bronchus Displaced Supernumerary Tracheal diverticula If the anatomic upper-lobe bronchus is missing a single branch Supernumerary If the right upper-lobe bronchus has a normal trifurcation into apical, posterior, and anterior segmental bronchi Tracheal diverticula If the supernumerary bronchi end blindly Apical accessory lungs or tracheal lobes If they end in aerated or bronchiectatic lung tissue The displaced type of tracheal bronchus is more frequent than the supernumerary type

Tracheal Bronchus Patients are usually asymptomatic Persistent or recurrent upper-lobe pneumonia, atelectasis or air trapping, and chronic bronchitis Bronchiectasis, focal emphysema, and cystic lung malformations may coexist

Tracheal Bronchus Chest CT A small area of hypoattenuation arising directly from the trachea

Tracheal Bronchus Bronchography and bronchoscopy allow the direct visualization of the ectopic bronchus

Bronchial Atresia Results from focal obliteration of a proximal segmental or subsegmental bronchus that lacks communication with the central airways The bronchi distal to the stenosis become filled with mucus and form a bronchocele The alveoli are ventilated by collateral pathways and show features of air-trapping The upper-lobe is more frequently affected May be acquired postnatally owing to traumatic or postinflammatory insult to the bronchus Most often affects segmental bronchi at or near their origin; however, lobar or subsegmental bronchi may also be involved The abnormality is an incidental finding in approximately 50% of cases, mostly in young men

Bronchial Atresia In the newborn period Later in childhood In adults Bronchial atresia is seen as a water-density mass Later in childhood Bronchial atresia is found because of focal air trapping In adults Bronchial atresia is seen as a solitary pulmonary nodule due to a mucus plug The mass is fetal lung liquid trapped behind the atresia The short atretic segment leads to accumulation of mucus within the distal bronchi to form a bronchocele, and underventilation of the affected part of the lung occurs

Bronchial Atresia CT is a sensitive modality It shows a round opacity at the site of the atresia, medial to the air trapping The characteristic chest radiographic finding consists of a bronchocele, seen as rounded, branching opacities radiating from the hilum. The bronchocele may contain an air-fluid level. The distal lung is emphysematous and produces an area of hyperlucency around the affected bronchi. In newborns, the affected segment may be seen as a fluid-filled mass

Bronchogenic Cyst Originate from the primitive ventral foregut Location Mediastinal: paratracheal (usually right-sided), carinal, or hilar Intrapulmonary: medial third of the lung, lower lobes Lower neck Account for 40%~50% of all congenital mediastinal cysts There is a slight male predominance Approximately two-thirds are within the mediastinum, and one-third are intraparenchymal The carinal location is most frequent

Bronchogenic Cyst The cysts contain mucoid material and are lined by ciliated columnar or cuboidal epithelium Their walls contain smooth muscle and cartilage Do not initially communicate with the tracheobronchial tree Two-thirds of the patients are symptomatic Caused by compression of the trachea or bronchi Infection occurs in 20% of patients with intraparenchymal cysts Instrumentation of the cyst or infection may lead to air-filled cyst or an air-fluid level However, most bronchogenic cysts in children are found incidentally when imaging is performed for other reasons

Bronchogenic Cyst In infants and children, the chest radiograph is diagnostic Appear as water-density mass lesions Show no contrast enhancement

Bronchogenic Cyst Intrapulmonary cysts may show air or an air-fluid level When they become infected they may show wall enhancement

Anomalies of the Lung Pulmonary Underdevelopment Scimitar Syndrome Congenital Cystic Adenomatoid Malformation Congenital Lobar Emphysema Pulmonary Sequestration

Pulmonary Underdevelopment Classified into three groups Group 1, bronchus and lung are absent (agenesis) Group 2, a rudimentary bronchus is present and limited to a blind-end pouch without lung tissue (aplasia) Group 3, there is bronchial hypoplasia with variable reduction of lung tissue (hypoplasia) The abnormality is usually unilateral The contralateral lung is normal in structure but has compensatory hypertrophy

Pulmonary Agenesis Ocasionally, the agenesis may be confined to one lobe (left upper lobe) More than 50% have associated congenital anomalies Cardiovascular (PDA and patent foramen ovale), gastrointestinal, skeletal, and genitourinary systems Patients with right-lung agenesis have a shorter life expentancy The etiology of lung agenesis is unknown, although genetic, teratogenic, and mechanical factors have been proposed as possible causes there is no side or gender predominance Most of the limb and spinal anomalies are ipsilateral to the pulmonary agenesis, whereas the rib anomalies are variable this suggests that the right-lung agenesis has a greater frequency of an associated shift of the heart and mediastinum, with corresponding distortion of bloods vessel and bronchi

Pulmonary Agenesis A small, completely opaque hemithorax with displacement of the mediastinal structures and diaphragm CT angiography and MR angiography are currently the imaging modalities of choice

Pulmonary Hypoplasia Caused by factors compromising the thoracic space available for lung growth Extrathoracic causes: oligohydramnios Intrathoracic causes: congenital diaphragmatic hernia Extralobar sequestration: agenesis of the diaphragm, large pleural effusion Other causes: decreased pulmonary vascular perfusion (tetralogy of Fallot, unilateral absence of the pulmonary artery) (Potter syndrome: renal agenesis, abnormal fasciae, limb anomalies, and bilateral pulmonary hypoplasia) Jeune syndrome (asphyxiating thoracic dystrophy)

Pulmonary Hypoplasia In cases of premature rupture of membranes at 15~28 weeks gestation, the reported prevalence of pulmonary hypoplasia ranges from 9% to 28% Manifestation Early respiratory distress after birth, cyanosis, tachypnea, hypoxia, hypercapnea, and acidosis Pneumothorax and pulmonary hypertension are common serious complications Pneumothorax often develops spontaneously or secondary to mechanical ventilation

Pulmonary Hypoplasia Plain radiographs Decreased aeration of the affected hemithorax (more frequent in the right lung) and a small thoracic cage Displacement of the mediastinum to the side of the hypoplasia In some cases, a cystic appearance is encountered, which could be due to a developmental defect at the bronchioloalveolar junction (congenital bronchiectasis)

Scimitar Syndrome Also called venolobar syndrome and hypogenetic lung syndrome Anomalous systemic arterial supply to the lower lobe of the right lung from the subdiaphragmatic aorta or its main branches Ipsilateral anomalous pulmonary drainage of part or all of the right lung into the inferior vena cava Hypoplasia or other malformation of the right pulmonary artery Dextrorotation of the heart Hypoplasia of the right lung is a congenital cardiovascular anomaly involving the right lung

Scimitar Syndrome Three forms The infantile form: a large shunt between the abnormal artery that supplies the lower lobe of the right lung and the subdiaphragmatic aorta In the adult form: a small shunt between the right pulmonary veins and inferior vena cava The third form: additional cardiac and extracardiac malformations Associated with abnormal bronchial anatomy, abnormal diaphragm, hemivertebrae, and anomalies of the genitourinary tract

Scimitar Syndrome At least 40% of patients are asymptomatic The clinical symptoms usually manifest in the 2nd to 3rd decade of life Fatigue and dyspnea with exertion Recurrent pulmonary infection In the infantile group, a higher prevalence of pulmonary hypertension has been reported The clinical significance and prognosis depend to a large extent on the amount of the resulting left-right shunt

Scimitar Syndrome The pulmonary vein descending along the right cardiac border (scimitar sign)

Congenital Cystic Adenomatoid Malformation An overgrowth of bronchioles, with almost complete suppression of alveolar development between the 7th and 10th weeks of embryonic life Characterized by a multicystic mass of pulmonary tissue with an abnormal proliferation of bronchial structures It usually involves a single lobe

Congenital Cystic Adenomatoid Malformation Classified into three histologic types Type I: variable-size cysts, with at least one dominant cyst (>2 cm in diameter), most common (75%) Type II: smaller, more uniform cysts less than 1 cm in diameter (10% to 15%) Type III: a solid mass composed of bronchoalveolar microcysts, often causes death at birth

Congenital Cystic Adenomatoid Malformation Type II Type I In older patients, cysts have an inflammatory component; this is due to the respiratory-lining and mucin-secreting cells In severe cases, the lung may be hyperexpanded, with mediastinal shift, a flat hemidiaphragm, and herniation of the lung to the contralateral side Type III Type I

Congenital Cystic Adenomatoid Malformation Symptoms Prenatal: broad variation, ranging from an incidental finding to severe hydrops with mass effect and mediastinal shift Postnatal: 1/2~2/3 will have some form of respiratory distress or compromise, including tachypnea, retractions, and cyanosis Older patients: recurrent pulmonary infections

Congenital Lobar Emphysema Result from a check-valve mechanism at the bronchial level that causes progressive hyperinflaction of the lung Characterized by progressive overdistention of a lobe, sometimes two lobes The most commonly affected lobe is the left upper lobe (42.2%), followed by the right middle lobe (35.3%), the right upper lobe (20.7%), and in each lower lobe (0.9%)

Congenital Lobar Emphysema It is more common among males May be associated with other anomalies (cardiovascular system is involved in 12%~14%) Most patients become symptomatic during the neonatal period, most before 6 months of age Respiratory distress is the most common It becomes symptomatic in infancy (type I), in older children (type II), or is an incidental finding in asymptomatic patients (type III) In 50%~55% of cases, the cause of congenital lobar emphysema is unknown Areas of malacia or stenosis of the bronchial cartilage were found

Congenital Lobar Emphysema Congenital lobar emphysema may be confused with pneumothorax or with a simple lung cyst or acquired cyst Ipsilateral and contralateral atelectasis may occur If the affected lobe is large and markedly expanded, the ipsilateral ribs may be separated and the hemidiaphragm depressed There are bronchovascular markings within the overdistended lobe, and the adjacent lobe collapses are either caudad or cephalad but not medial, toward the hilum

Pulmonary Sequestration Defined as an aberrant lung tissue mass that has no normal connection with the bronchial tree or with the pulmonary arteries Arterial blood supply arises from the systemic arteries, usually the thoracic or abdominal aorta Venous drainage is via the azygous system, the pulmonary veins, or the inferior vena cava Divided into two types: extralobar and intrapulmonary

Intralobar Sequestration Contained within the lung and has a visceral pleura covering It is located within the lower lobe in 98% of cases It usually contains air within cystic lung tissue or air-fluid levels when infections are present It is usually considered an acquired abnormality of the lung, due to recurrent infections and bronchial obstruction

Extralobar Sequestration It is a mass of abnormal lung tissue that is surrounded by its own separate pleura It is usually located in the posterior lower chest, and 90% are located on the left side It is more common Associated with diaphragmatic hernia, congenital heart disease, and congenital cystic adenomatoid malformation Male : Female = 4 : 1

Pulmonary Sequestration It has the appearance of a soft-tissue opacity in the posterior basal segment of the lung, with smooth or lobulated margins Brochiectasis, subsegmental atelectasis, mediastinal shift, and prominence of the ipsilateral hilum are additional radiographic findings

Pulmonary Sequestration CT scans show a soft-tissue cystic mass containing air or fluid, focal emphysema, and a hypervascular focus of lung tissue

Esophageal Anomalies Esophageal Atresia and Tracheoesophageal Fistula Esophageal Duplications

Esophageal Atresia and Tracheoesophageal Fistula It is the most common congenital malformation of the esophagus It is thought to be due to a developmental disorder in formation and separation of the primitive foregut into trachea and esophagus Intrauterine anoxia or stress with resulting vascular compromise may produce focal necrosis of the esophagus

Esophageal Atresia and Tracheoesophageal Fistula In 25% of cases, it is associated with other gastrointestinal malformations such as imperforate anus, pyloric stenosis, duodenal atresia, annular pancreas The "VACTERL" complex (vertebral, anal, cardiovascular, tracheoesophageal, renal, radial, and limb malformations)

Esophageal Atresia and Tracheoesophageal Fistula It is generally suspected on the basis of polyhydramnios, inability to swallow saliva or milk, aspiration during early feedings, or failure to successfully pass a catheter into the stomach Atelectasis and pneumonia involving the upper right lobe are seen in up to 50% of cases

Esophageal Atresia and Tracheoesophageal Fistula A blind pouch of the proximal esophagus, distended with air Include the abdomen to look for the presence of air in the gastrointestinal tract

Esophageal Duplications It is the second most common duplications of the gastrointestinal tract after those of the ileum The duplicated segment has a thick wall of smooth muscle and is lined with alimentary tract mucosa Complete duplication is a rare malformation, often associated with gastric duplication In the newborn and infant, symptoms are due to pressure on the adjacent lung or esophagus The aberrant luminal recanalization theory proposed by Bremer is an adequate explanation for duplications in those portions of the gastrointestinal tract that go through the "solid stage," such as the esophagus, small bowel, and colon

Esophageal Duplications Most often, duplications are spherical cysts and are usually located in the right hemithorax On plain chest radiographs, they are usually seen as posterior mediastinal masses In cystic esophageal duplication, the esophagogram shows the esophagus to be displaced to the side opposite the cystic mass or an intramural extramucosal mass

Esophageal Duplications A duplication is sharply marginated, has a homogeneous near-water density, and is not enhanced after intravenous contrast material injection Endoscopic sonography has proved to be a reliable method because it can demonstrate contiguity of the muscularis propria of the esophagus with the muscle layer of the cyst wall