Anomalous unilateral single pulmonary vein: two cases mimicking arteriovenous malformations and a review of the literature.

Total anomalous pulmonary venous drainage is a rare congenital anomaly. It usually involves a pulmonary to systemic venous shunt and most cases have a septal defect in order to survive. Anomalous pulmonary venous drainage with pulmonary venous shunting is an extremely rare and entirely benign entity. We present two such cases, in which there was atresia of the left superior pulmonary vein and drainage via a tortuous collateral vein to the left inferior pulmonary vein. This collateral was mistaken on plain film and CT for a pulmonary arteriovenous malformation. Awareness of this anomalous unilateral single pulmonary vein and its radiological appearances may help in avoiding unnecessary pulmonary angiography.