Congenital and Developmental Diseases of the Lungs and Airways

Chest Radiography

In patients with congenital lung disease, the chest radiograph is frequently the initial examination performed. A typical scenario is a patient referred for chest radiography for productive cough, dyspnea, chest pain, or fever who is discovered to have a congenital lung abnormality. The clinical symptoms observed may or may not be related to the congenital lung disease. Although the chest radiograph may be suggestive for a particular congenital lung disease, cross-sectional imaging (CT or MRI) is usually required to confirm the diagnosis and to evaluate for associated abnormalities.

After the diagnosis is established, the chest radiograph may be used to monitor the stability of the lesion and evaluate for complications such as superimposed infection if clinical symptoms arise. If the patient is to undergo surgical resection, the patient may undergo chest radiography during the preoperative workup.

Chest CT and CT Angiography

CT of the chest is the most common modality used to evaluate and diagnose congenital lung disease. Due to the high spatial resolution of chest CT, it is well suited to illustrate the nature and anatomic considerations of congenital lung lesions. This includes evaluation of the anatomic location, extent of the lesion, nature of the lesion, bronchial supply, arterial supply, and venous drainage. CT angiography (CTA) is useful in cases that are vascular in nature or have important vascular anatomy. The bolus timing of the CTA should be determined by the suspected vascular supply of the lesion. For example, for lesions suspected to be of pulmonary artery origin (e.g., a pulmonary arteriovenous malformation), a bolus timing technique timed to peak enhancement of the pulmonary arteries (similar to the CT pulmonary embolism protocol) may be chosen. For lesions suspected to be of systemic arterial origin (e.g., a bronchopulmonary sequestration), a bolus timing technique timed to the descending aorta may be chosen.

Thoracic MRI and MR Angiography

MRI of the chest can also be used to evaluate congenital lung lesions, especially for younger patients in whom radiation is an important clinical concern. However, MRI is not as useful for evaluation of the lung and airways. Therefore, chest CT with IV contrast is usually chosen as the initial modality for evaluation of adult patients with suspected congenital lung disease.

However, thoracic MRI excels at evaluation of cystic lesions in the mediastinum. Therefore, thoracic MRI may be used as the primary imaging modality for the evaluation of suspected mediastinal foregut duplication cysts, such as bronchogenic or esophageal duplication cysts. Mediastinal MRI is very useful as a problem-solving technique in patients with a suspected cystic mediastinal lesion on CT but for whom the measured CT attenuation values are not diagnostic for a cyst. MRI is an excellent modality to differentiate cystic and solid lesions. MRI of the thorax performed pre- and post­gadolinium, with subtraction of precontrast from the postcontrast signal, can detect even a subtle enhancing component.

MR angiography (MRA) is sometimes used to define the arterial supply of a lung or mediastinal lesion when the arterial supply is suspected to be of systemic origin. To ensure adequate spatial resolution and avoid respiratory or cardiac motion artifacts, thoracic MRA requires meticulous technique, particularly for smaller vessels. For these reasons, and for evaluation of the airways, chest CTA is usually preferred due to its higher spatial resolution, speed, and ease of imaging.

Catheter Angiography

Catheter angiography can also be used to define the arterial supply, venous drainage, and general vascularity of a congenital lung lesion. Catheter angiography is most often used as a problem-solving technique in patients in whom the vascular anatomy requires further definition prior to surgical resection. Occasionally, congenital lung lesions are embolized as a primary therapy or prior to surgical resection. In these circumstances, angiography will be performed prior to embolization.

Bronchopulmonary Sequestration

A bronchopulmonary sequestration is a mass of abnormal lung tissue that lacks normal communication with the tracheobronchial tree. The mass usually consists of abnormal, nonfunctioning lung tissue that derives its arterial supply from a systemic artery rather than a pulmonary artery. The systemic artery may be a single systemic artery or multiple arteries most commonly arising from the descending aorta, but may arise from the abdominal aorta, celiac artery, splenic artery, or rarely an intercostal artery. The identification of the systemic artery is a key feature for diagnosis of bronchopulmonary sequestration on imaging ( Fig. 15.1A–D ).

Imaging Appearance

Intralobar sequestrations may present as a solid mass or cystic mass. Cystic intralobar sequestrations may contain air cysts, fluid cysts, or both air- and fluid-filled cysts and there may be air-fluid levels (see Fig. 15.1E–H ). Rarely, an intralobar sequestration may present as a focal area of hyperinflated lung. Extralobar sequestration typically presents as a solid vascular mass in the lung base, near the hemidiaphragm ( Fig. 15.2 ). In all cases of sequestration, a systemic artery is present, and normal bronchial communication is absent.

Congenital Pulmonary Airway Malformation

Congenital pulmonary airway malformations (CPAMs) comprise a spectrum of airway malformations (hamartomas) that involve various portions of the tracheobronchial tree. CPAMs were previously referred to as congenital cystic adenomatoid malformations (CCAMs), but the name of the disease has been changed because not all these lesions are adenomatoid or cystic. The classification scheme for CPAMs has also been expanded, and there are now five types of CPAM based on the pathologic site of origin of the lesion in the tracheobronchial tree:

• Type 0: Airway malformations of the proximal tracheobronchial tree

• Type 1: Airway malformations of bronchial or bronchiolar origin (large cyst lesion)

• Type 2: Airway malformations of bronchiolar origin (the small cyst lesion)

• Type 3: Airway malformations of bronchiolar or alveolar duct origin (the adenomatoid lesion)

• Type 4: Airway malformations of distal acinar or alveolar origin (the unlined cyst lesion)

Imaging Appearance

Usually CPAMs present early in life but have been reported in adult patients. At imaging, CPAMs usually present as a cystic mass ( Fig. 15.3 ), but occasionally appear solid. If the largest cyst is >2.5 cm, these tend to be type 1 CPAMs. If the cysts are <2.5 cm or the lesion is solid, it is difficult to predict the subtype of CPAM. The diagnosis of a CPAM in an adult patient is controversial due to overlap of the imaging features of CPAM and lung injury or repair, which may result in cystic lesions or pneumatoceles. Usually, CPAMs have normal arterial and venous connections, differentiating CPAM from bronchopulmonary sequestration.