Congenital pulmonary malformations are relatively rare entities that can cause a wide variety of pulmonary findings in infants and children. In this chapter, we review the clinical and radiographic features of the most important malformations, including:

1. Congenital absence of the pulmonary vein

2. Tracheal bronchus

3. Bronchial cyst

4. Congenital lobar emphysema

5. Congenital cystic adenomatoid malformation

6. Pulmonary sequestration

7. Pulmonary agenesis

Patient Story

A 5 year-old-girl is hospitalized for respiratory distress and hypoxemia. This is her third episode of right-sided pneumonia. She is thinly built; both height and weight are at the 25th percentile for age. Chest auscultation reveals fine alveolar crackles over the entire right lung without wheeze; the left lung is clear. Heart sounds are normal without a murmur. Her chest x-ray shows haziness of the entire right lung, with patchy opacity in the right lower zone; the left lung is normal. She is treated with parenteral antibiotics and improves. Blood and sputum cultures are negative. She is evaluated further for recurrent pneumonia. Serum immunoglobulin profile is normal. Sweat chloride is within normal limits. Chest CT scan with contrast shows Swiss cheese appearance of the entire right lung with cystic lucencies and septal thickening; the left lung is normal (Figure 52-1). Further cardiac evaluation with Echocardiography shows no intra-cardiac defect. Cardiac catheterization and pulmonary angiography reveal normal pulmonary artery anatomy, with isolated absence of the right main pulmonary vein. She is followed closely and her subsequent respiratory illnesses are treated early with antibiotics and bronchodilators. She remains asymptomatic with exercise tolerance and growth appropriate for age.

Introduction

Unilateral absence of the pulmonary vein is a rare congenital abnormality thought to be due to atresia of the pulmonary vein during development in the prenatal period. This results in abnormal venous drainage of the affected lung and significant ventilation perfusion mismatch.

Synonym

Congenital unilateral pulmonary vein agenesis.

Epidemiology

• Congenital absence of the pulmonary vein is a rare congenital anomaly, found in about 0.5 percent of autopsies performed in children.

• May occur as an isolated lesion or associated with other congenital cardiac defects in about 30 to 50 percent of cases.

• Mortality rate approaches 50 percent if untreated.

Etiology and Pathophysiology

• Rare developmental abnormality, in which there is absence of the right or left pulmonary vein or both.

• Thought to result from failure of incorporation of the pulmonary vein into the left atrium.

• There is a spectrum of disease: lesser degrees of venous atresia result in pulmonary vein stenosis with narrowing, venous obstruction and anatomic variations in the pulmonary vessels that drain the affected lung to complete absence of the affected pulmonary vein.

• Pulmonary venous obstruction from the intra-uterine period affects normal development and architecture of the lung, leading to engorgement of bronchial veins, chronic pulmonary edema, lymphatic dilatation, inter-alveolar septal thickening, patchy interstitial fibrosis, cystic changes, and development of collateral vessels.

• Inadequate gas exchange occurs at the alveolar level of the entire affected lung, resulting in large dead space ineffective ventilation and significant ventilation perfusion mismatch.

Diagnosis

The diagnosis is often elusive and difficult to make; it requires a high index of suspicion when a patient presents with the clinical history of recurrent pneumonia together with asymmetry of lung aeration with reticular interstitial infiltrates on imaging. This should prompt further investigation with CT scan and pulmonary angiography.

Clinical Features

• Presentation is often in infancy or early childhood (usually less than 5 years age).

• Typical symptoms include recurrent unilateral respiratory infections/pneumonia and exercise intolerance with dyspnea on exertion.¹

• Occasionally, hemoptysis may be a presenting symptom.

• As the pulmonary circulation is suboptimal, infections can spread rapidly within the lung parenchyma with suppuration; repeated infections lead to bronchiectasis and chronic lung disease.

• Rarely, mildly symptomatic cases without associated cardiac defects or pulmonary hypertension can remain undetected and present later in adulthood.²

• Mortality approaches 50 percent if untreated.

• Complete atresia of the common pulmonary vein has been reported in the neonatal period presenting with severe respiratory distress, refractory hypoxemia, acidosis, pulmonary hypertension, and death, with diagnosis made at autopsy.

Imaging

Chest x-ray—Shows haziness of the entire affected lung with reticular opacities and septal prominence. The affected lung is reduced in volume with ipsilateral mediastinal shift at baseline. Opacification of the affected lung or lobar involvement with consolidation or suppuration may occur when symptomatic with lower respiratory infection.

• Shows asymmetry with small hemithorax due to reduced lung volume, and ground-glass haziness with interlobular septal thickening throughout the affected lung (Figure 52-1).

• Interstitial fibrosis can occur secondary to pulmonary venous infarction and chronic pulmonary edema.

• There may be an ipsilateral small pulmonary artery with aberrant systemic arterial supply to the affected lung.

• The bronchial anatomy and patency are normal.³

• Of note, multidetector CT noninvasively demonstrates the anatomy and may obviate the need for invasive angiography.⁴

Magnetic resonance imaging—Confirms hypoplasia of affected lung, with diffuse interstitial thickening, pulmonary edema, and engorgement of pulmonary lymphatics.

Ventilation perfusion scan—Shows marked reduction in ventilation and perfusion to the affected side without air trapping.

Bronchoscopy—Shows normal tracheal and bronchial anatomy.

Cardiac catheterization—Pulmonary angiography is used for definitive diagnosis with characteristic findings: markedly increased pulmonary capillary wedge pressures, small ipsilateral pulmonary artery, and absence of the pulmonary vein on venous phase imaging.⁵

Histopathology

The pulmonary parenchyma shows patchy interstitial fibrosis, pulmonary arteries show medical muscular hypertrophy. The pulmonary veins show medial muscular hypertrophy with intimal fibrosis and luminal narrowing without inflammatory change.

Differential Diagnosis

• Pulmonary lymphangiectasia—Usually distinguished by the radiographic appearance of the lymphatic malformation.

Management

Nonpharmacologic

• Attention to nutritional intake for optimal somatic and lung growth and development and recovery from infection.

• Chest physiotherapy for airway clearance with respiratory illnesses.

• Inhaled bronchodilators if there is associated bronchospasm or wheeze.

• Immunization—In addition to routine childhood immunizations, annual influenza vaccine after age 6 months, 23-valent pneumococcal vaccine for children aged >2 years every 5 years.

Medications

• Early appropriate antibiotic therapy for lower respiratory infections; antibiotics tailored to known bacterial pathogens according to age.

• Aggressive approach in treating respiratory infections is essential to avoid suppurative complications; parenteral antibiotics when dictated by clinical presentation and radiological findings on chest x-ray.

Surgery

• Anastomosis of the atretic pulmonary vein to the left atrium is a theoretical consideration but may not be possible due to complex and abnormal vascular anatomy.

• Pneumonectomy is recommended if there are recurrent or chronic suppurative complications or if the affected lung becomes a nidus of infection.⁶ Pneumonectomy effectively eliminates the dead space and left to right shunt that may have developed.

Referral

• Pediatric Cardiology—For (1) echocardiography to screen for associated congenital heart defects and (2) Cardiac catheterization and pulmonary angiography, measurement of pulmonary capillary wedge pressures for definitive diagnosis.

• Pediatric Pulmonology—To effectively manage recurrent respiratory infections, chest physiotherapy for airway clearance and to monitor pulmonary function longitudinally.

Prevention and Screening

Maintain high index of suspicion and screen children with history of recurrent unilateral pneumonia with or without hemoptysis in early infancy or childhood with chest CT with contrast.

Prognosis

• Prognosis following pneumonectomy is excellent with good functionality.

• Post-pneumonectomy, there is potential for scoliosis to develop in the growing child. Plombage (in which the empty hemithorax is filled with an inert material, e.g., sterile Lucite balls) is an option to maintain thoracic volume and prevent/minimize scoliosis.

• Mortality approaches 50 percent if left untreated.

Follow-Up

• Optimize nutrition for lung growth and development.

• Annual cardiac screening with ECHO to monitor for pulmonary hypertension and right heart strain secondary to repeated lung infections.

Patient Story

A 17-year-old boy with Type 1 neurofibromatosis, seizure disorder, developmental delay, and dysphagia presents in winter with high-grade fever, cough, and respiratory distress. On examination he appears toxic and is tachycardic and tachypneic with intercostal and subcostal retractions. He requires oxygen via facemask at 5 liters/minute to maintain pulse oximetry saturations above 92 percent. Chest auscultation reveals scattered crackles and expiratory rhonchi over both lung fields. Rapid viral screen for influenza (H1N1) virus is positive. Chest x-ray shows right upper lobe consolidation and bibasilar patchy infiltrates. Laboratory investigations show an elevated white count and blood culture is negative. He is treated with broad spectrum parenteral antibiotics, oral oseltamivir, inhaled bronchodilators, and aggressive chest physiotherapy for airway clearance. He improves with weaning in his oxygen requirement to room air. Serial chest x-rays show right upper lobe collapse, which persists despite clinical improvement, even a month after discharge home. Further imaging with chest CT with contrast is done, which shows a tracheal bronchus supplying the right upper lobe, with a mucus plug obstructing the aberrant tracheal bronchus lumen (Figure 52-2). As he is asymptomatic and clinically stable, he is continued on chest physiotherapy with manual clapping and inhaled bronchodilators. A follow-up chest x-ray 2 months later shows resolution of the right upper lobe atelectasis with well aerated lung fields bilaterally.

Introduction

Tracheal bronchus describes a variety of bronchial anomalies, which arise from the main trachea proximal to the carina. An aberrant tracheal bronchus to the right upper lobe of the lung arises directly from the trachea itself proximal to the carina, unlike its typical origin after tracheal bifurcation, from the right main bronchus.

Synonyms

Bronchus suis, Pig bronchus.

Epidemiology

• An aberrant tracheal bronchus is often detected incidentally on CT imaging of the chest or bronchoscopy, and occurs in about 2 percent of the population.

• The right tracheal bronchus may be displaced in its origin to arise from the mainstem of the trachea proximal to the carina (a “pig bronchus” with all three segmental branches from it with no connection of the right upper lobe to the right main bronchus) or it may consist of only the right upper lobe apical bronchus with anterior and posterior segmental upper lobe branches arising from the right main bronchus.

• A prevalence of 0.1 to 2 percent for right tracheal bronchus and 0.3 to 1 percent for left tracheal bronchus have been reported in bronchoscopic and imaging studies.⁷

• Very rarely, bilateral tracheal bronchi may occur directed to both upper lobes of the lung.

• Tracheal bronchus has been found in association with other congenital anomalies including trachea-esophageal fistula, tracheal stenosis, VATER syndrome (vertebral anomalies, anal atresia, trachea-esophageal fistula, esophageal atresia, renal defects), and Trisomy 21.

Etiology and Pathophysiology

• Embryogenic hypotheses for this congenital bronchial abnormality are the reduction, selection and theories of bronchial bud development (that the final anatomy is the result of shrinkage, suppression of portions of the original distribution and movement/migration from the initial location to arise from new origins) resulting in local disturbances in morphogenesis.⁷

• Altered drainage of the affected right upper lobe can result in localized pulmonary problems: partly due to the more horizontal direction of the tracheal bronchus, which impairs airway clearance as compared to the more vertical and gravitationally assisted normal configuration of the right upper lobe bronchus.

• This may result in localized or persistent atelectasis of the right upper lobe and recurrent infections with potential for suppurative changes and development of bronchiectasis.

• Both the pulmonary and bronchial vascular supply to the affected lobe of the lung are normal.

Diagnosis

Tracheal bronchus is now diagnosed with increased frequency as a result of advances in and availability of chest CT imaging. Bronchoscopic examination of the airways is definitive, clearly demonstrating the tracheal origin of the aberrant bronchus.

Clinical Features

• Often asymptomatic; may be detected incidentally on imaging or bronchoscopic examination.

• May cause recurrent infection, atelectasis, or consolidation of the right upper lobe due to mucus plugging and/or retained airway secretions.⁸

• Persistent cough may be a symptom. Occasionally hemoptysis may occur.

• Bronchiectatic changes may occur with repeated infections.

• If unrecognized, it may be the cause of persistent right upper lobe atelectasis/collapse in intubated patients due to occlusion of the orifice of the aberrant tracheal bronchus by the endotracheal tube.⁹ Occasionally, inadvertent intubation of the aberrant bronchus may occur resulting in impaired ventilation.

Imaging

• Chest x-ray—Right upper lobe atelectasis/collapse with lobar opacification that may be recurrent or persistent in nature.

• Chest CT scan—Shows the origin of the aberrant tracheal bronchus proximal to the carina; the rest of the bronchial anatomy is normal with normal lung parenchyma.¹⁰ CT virtual bronchoscopy is a non-invasive alternative for diagnosis.

• Bronchoscopy—Definitive diagnosis rests on bronchoscopic examination of the airway, and visualization of the origin of the aberrant bronchus from the tracheal lumen proximal to the carina.¹¹

Differential Diagnosis

• Supernumerary tracheal bronchus—This occurs in addition to the normally originating right upper lobe bronchus arising from the right main bronchus.

• Accessory bronchus—Will be seen on radiographic imaging.

Management

• Although asymptomatic and often incidentally detected, if present it can impact the care of children undergoing anesthesia and intubation and post-operative recovery. This airway anomaly must be kept in mind when chronic right upper lobe atelectasis/collapse is noted.⁹

• Management is based on the severity and frequency of associated symptoms.

• Surgical resection of the anomalous bronchus and lobe is indicated if recurrent suppurative infections occur.

• In asymptomatic or infrequently symptomatic patients, conservative and expectant management with antibiotics, chest physiotherapy and airway clearance are preferred.

Nonpharmacologic

• Care must be taken when intubation is being performed especially in children with conditions known to be associated with tracheal bronchus, including Down syndrome, foregut malformations, and tracheal stenosis.

• Chest physiotherapy regimen for airway clearance.

Medications

• Inhaled bronchodilators may be used to aid mucociliary clearance and augment chest physiotherapy maneuvers.

Surgery

• Right upper lobectomy is indicated if there is recurrent suppurative lung disease secondary to bronchial obstruction and impaired drainage of secretion.

Referral

Physiotherapist—To teach parent/caregiver chest physiotherapy for airway clearance, instruct patient in use of airway clearance devices using positive end-expiratory pressure, that is, Acapella or Flutter device.

Prevention and Screening

Tracheal bronchus should be screened for in children presenting with recurrent right upper lobe pneumonia or collapse, particularly if there are other associated congenital malformations of the heart, vertebrae, and gastrointestinal tract.

Prognosis

Risk of recurrent respiratory infections due to obstruction of tracheal bronchus. Prognosis is good following surgical intervention with lobectomy.

Patient Story

A healthy, athletic 16-year-old-girl presented with acute right lower abdominal pain and vomiting for one day. She was evaluated with an abdominal CT scan with contrast which ruled out acute appendicitis. Incidentally, the lower thoracic cuts of the CT scan showed a low density mass inferior to the left mainstem bronchus (Figure 52-3). There were no lung parenchymal abnormalities, no adenopathy or effusion noted. She reported no symptoms, her lungs were clear on auscultation and spirometry revealed normal lung function and capacities. A chest MRI was done which showed a 40 × 30 × 37 mm mass with increased signal intensity located between the left inferior pulmonary vein and the descending thoracic aorta without contrast enhancement following administration of gadolinium (Figure 52-4). This cystic infrahilar mass appeared most compatible with a bronchogenic cyst. Elective surgical resection of the cyst was done successfully via thoracotomy; histopathology showed ciliated respiratory epithelium with goblet cells without metaplasia. She recovered uneventfully, was asymptomatic and returned to sport with normal exercise tolerance.

Introduction

• Bronchogenic cysts result from abnormal branching or budding of the ventral diverticulum of the foregut during embryologic development of the tracheobronchial tree.¹²

• Most often unilocular and lined with pseudo-stratified columnar respiratory epithelium, with a fibrovascular connective tissue wall of hyaline cartilage, smooth muscle and mucus glands.

• Do not usually communicate with the bronchial tree and therefore not typically air filled. They contain fluid (water), with variable amounts of proteinaceous material.

Synonyms

• Foregut duplication cyst.

Epidemiology

• Bronchogenic cysts comprise approximately 6 percent to 15 percent of primary mediastinal masses. Most often detected incidentally upon routine chest radiography.

• Tend to be detected more commonly in the right chest and more often in males.¹

Etiology and Pathophysiology

• Bronchogenic cysts are characteristically oval or round in shape and occur in various locations depending on the stage of embryogenesis in which their formation occurs.

• Most commonly located in the mediastinum (paratracheal, pericarinal), intrapulmonary, and extrathoracic (para-esophageal and even subdiaphragmatic).

• Often asymptomatic, but have the potential to enlarge and compress adjacent structures in the mediastinum.

• Infection and rupture of the cyst can result in mediastinitis.

Diagnosis

Usually suspected from its appearance on chest radiograph as a well marginated opacity of fluid attenuation. Definitive diagnosis can only be made by surgical excision and histopathological confirmation of the cyst lining as pseudo-stratified ciliated epithelium and wall containing cartilage, smooth muscle, or mucus glands.

Clinical Features

• Usually benign congenital masses, which are asymptomatic; most commonly mediastinal in location.

• Clinical presentation varies from asymptomatic with incidental detection on imaging, to symptomatic large masses causing compression of adjacent structures.¹³

• Complete bronchial obstruction due to compression can lead to atelectasis of the lung; or air trapping if partial bronchial obstruction.

• Potential for infection of the cyst, resulting in fever, cough, dyspnea, and chest pain. Occasionally life-threatening hemoptysis or mediastinitis may occur.¹³ Repeated cyst infection and inflammation can result in pericystic adhesions, ulceration of the cyst wall, and fistulous connection with the bronchial tree.

• Rarely, metaplasia may occur in the cyst lining, with malignant degeneration, and potential for development of bronchioalveolar carcinoma.

Distribution

• Bronchogenic cysts can be broadly classified as mediastinal and intrapulmonary.

• Most common location is middle mediastinum (2/3)—Typically these cysts do not communicate with the tracheobronchial tree, and can be hilar, paratracheal, or subcarinal in location.

• Intrapulmonary or parenchymal (1/3)—Typically perihilar with a predilection for the lower lobes of the lung, and cyst lumen may communicate with the tracheobronchial tree.