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Pulmonary aplasia

Dr Yuranga Weerakkody and Dr Maxime St-Amant et al.

Pulmonary aplasia is a rare congenital pathology in which there is unilateral or bilateral absence of lung tissue. It is distinguished from pulmonary agenesis, although similar, the main difference being that there is a short-blind ending bronchus in aplasia ³.

It is usually unilateral, as bilateral pulmonary aplasia is not viable. It is frequently associated with other congenital abnormalities, mainly cardiovascular, and has been reported to occur with VACTERL syndrome ¹.

Clinical presentation

Pulmonary aplasia usually presents with neonatal respiratory distress of variable intensity ². In rare cases, it may go unnoticed until later in childhood / adolescence ¹.

It can also be discovered during prenatal ultrasound screening, on which it presents as an hyperechoic hemithorax ². The diagnosis is frequently hard to make, but mediastinal shift will usually be prominent.

Pathology

Abnormal blood flow in the dorsal aortic arch during the 4th week of gestation had been hypothesized to cause pulmonary agenesis ³. The contralateral lung may develop as much as twice more alveoli in response to pulmonary aplasia / agenesis ¹.

Radiographic features

Plain film

On chest x-ray, it presents as an hemithorax white-out with ipsilateral shift of mediastinal structures and contralateral lung hyperinflation. A main ipsilateral bronchus is rarely seen, although CT-scan can demonstrate a rudimentary main bronchus ¹.

CT-scan

CT-scan will confirm the absence of lung parenchyma and mediastinal ipsilateral shift. Also, there is an ipsilateral absence of pulmonary artery. It may also show other cardiac congenital malformations and ipsilateral bronchus remnant.