Abnormal formation of lung tissue and bronchi and/or aberrant arterial blood supply to part of the lung results in a spectrum of anomalies that falls under the category of bronchopulmonary foregut malformations or dysplasias. Bronchopulmonary dysplasias result in lung masses that may replace a segment of lung, a lobe of lung, or an entire lung. Bronchopulmonary dysplasias can be further categorized into three types of lesions based on the characteristics of the lung parenchyma and on whether the arterial blood supply to the mass is systemic or pulmonary:

CPAM of the lung is a hamartoma of the lung resulting in a pulmonary mass that includes both cystic and solid components. The lesion usually contains multiple cysts of varying sizes. Cyst size is the basis for the categorization of CPAM into subtypes.

CPAMs are generally unilateral, often restricted to a single lobe. Their blood supply is from the pulmonary circulation. These lesions may communicate with the tracheobronchial tree. Type 3 CPAMs involving the entire lung may be identical to bronchial atresia at pathology and are considered by some to be the same entity.

CPAMs diagnosed in the second or early third trimester sometimes remain stable in size or become smaller as pregnancy proceeds. These lesions have an excellent prognosis, and they may be so small in relation to the normal lung at the time of birth that they cause no symptoms. Large CPAMs that do not regress may cause fetal hydrops and carry a worse prognosis.

A bronchopulmonary sequestration is a lobe or segment of lung with systemic blood supply (i.e., arterial supply from the aorta) and no communication with the tracheobronchial tree. The lung tissue does not typically contain cysts. A sequestration is more common in male than female fetuses and may be located either within the pleura that surrounds the normal lung (intralobar sequestration) or be covered by its own pleura (extralobar sequestration). It is generally unilateral. The most common location is in the left posterior lower thorax, but it can also be situated just below the left hemidiaphragm or on the right side. Like CPAMs, sequestrations diagnosed in utero sometimes decrease in size as pregnancy progresses.

Approximately half the masses of bronchopulmonary dysplasias are mixed lesions, characterized by abnormal lung tissue with cysts, like a CPAM, but receiving blood supply from the systemic circulation, like a sequestration. For this reason, careful assessment with both grayscale and color Doppler is important to establish the nature of the pulmonary lesion.

A CPAM appears sonographically as a unilateral pulmonary mass with one of the following characteristics:

Type 3 lesions have no visible cysts because the cysts are too small to be seen with ultrasound. When the entire lung is involved, the appearance of a type 3 malformation is the same as that of bronchial atresia.

B: Video clip through chest and upper abdomen demonstrating the cystic lung mass displacing the beating heart to the right.

Color Doppler can be used to determine that the blood supply to the mass arises from the pulmonary artery (Figure 10.1.4). In some cases, the cystic CPAM will decrease in size during gestation (Figure 10.1.5). In fetuses where the CPAM is large, it may cause


mediastinal shift or inversion of the diaphragm, and the fetus may have ascites, pleural effusions, or full-blown hydrops (Figure 10.1.6).

A bronchopulmonary sequestration appears on ultrasound as a homogeneously echogenic mass located either within the thorax (Figure 10.1.7) or just below the diaphragm (Figure 10.1.8). Color Doppler is used to identify the feeding artery from the aorta (Figure 10.1.7), confirming systemic blood supply. This finding helps distinguish a sequestration from a type 3 (microcystic) CPAM of the lung, which receives its blood supply from the pulmonary artery.

Mixed pulmonary lesions, those with characteristics of both CPAM and sequestration, appear as cystic lung masses with systemic arterial blood supply (Figure 10.1.9).