subsegmental pulmonary vein

A subsegmental pulmonary vein is a small pulmonary vein that drains oxygenated blood from a subsegment of the lung and empties into a segmental pulmonary vein, which in turn contributes to the main pulmonary veins returning blood to the left atrium.

A segmental pulmonary vein drains an entire bronchopulmonary segment of the lung, while a subsegmental pulmonary vein drains a smaller subdivision of that segment. Subsegmental veins converge to form segmental veins, which then form the larger lobar and main pulmonary veins.

The pulmonary veins are unique among veins in carrying oxygenated blood. After blood passes through the pulmonary capillaries where gas exchange occurs, it picks up oxygen from inhaled air and releases carbon dioxide. This oxygenated blood then flows into pulmonary venules and veins, ultimately returning to the left atrium.

On high-resolution CT scans of the chest, subsegmental pulmonary veins appear as small branching vascular structures within the lung parenchyma. Unlike bronchi and arteries which travel together in bronchoarterial bundles, pulmonary veins run interlobularly and are identified by their independent course away from the bronchi.

During anatomic lung resection, surgeons must identify and preserve or ligate subsegmental and segmental pulmonary veins. Inadvertent division of a vein draining a retained segment can cause venous congestion and infarction of that segment, while preserving correct venous drainage ensures adequate perfusion of the remaining lung tissue.