Opening of right inferior pulmonary vein

The opening of the right inferior pulmonary vein refers to the ostium (opening) where the right inferior pulmonary vein drains into the posterior wall of the left atrium.

In the classical anatomic pattern (present in approximately 71% of individuals), the right inferior pulmonary vein has a separate ostium with a mean diameter of 13.7 ± 3.3 mm. The ostium is located on the posteroinferior aspect of the left atrium, typically positioned below and separate from the right superior pulmonary vein ostium. The mean distance from the ostium to the first tributary branch is approximately 11.0 ± 3.7 mm, which is notably shorter than the left-sided pulmonary veins.

Anatomic variations are common and clinically important. The right inferior pulmonary vein frequently exhibits early branching (66-99% of cases), with multiple ramifications occurring close to the ostium. In some individuals, the middle lobe vein may drain into the right inferior pulmonary vein rather than the right superior pulmonary vein (occurring in 2.96-3.3% of cases). Less commonly, both right pulmonary veins may share a common ostium (<1% of cases).