Unilateral absence of a pulmonary artery (UAPA)

Imaging description Absence or proximal interruption of either the right or left pulmonary artery usually occurs within 1 cm of its origin from the main pulmonary artery [1]. More distal segments of the arteries in the hila are usually present, but are usually diminutive and are supplied by systemic collateral vessels which can arise from bronchial, internal mammary, and intercostal arteries. CT shows the abnormal termination of the pulmonary artery and the collateral vessels supplying the lung (Figure 52.1). Other findings include diminished pulmonary vascularity on that side, decreased size of the affected lung, and a contracted hemithorax. There is also resultant hyperexpansion of the contralateral lung. Left-sided UAPA is often associated with congential anomalies (Figure 52.2), particularly cardiac anomalies such as tetralogy of Fallot and septal defects. Right-sided UAPA is infrequently associated with other congenital anomalies, and is often referred to as isolated UAPA (IUAPA).