Medial vein of right lung

The medial vein of the right lung (V5; Medial part of the middle lobe vein)) drains the medial segment (S5) of the right middle lobe.

The right middle lobe venous drainage consists of medial and lateral parts (or medial and lateral veins) that show considerable anatomical variation in how they drain: 

Common drainage patterns include:

• Type I (53.3%): The medial and lateral parts unite to form a middle lobe vein trunk that drains into the right superior pulmonary vein

• Type II (16.6%): The medial and lateral parts drain separately into the right superior pulmonary vein

• Type III (16.6%): The medial and lateral parts unite to form a trunk that drains directly into the left atrium

• Type IV (10%): The medial and lateral parts drain separately into the left atrium

• Type V (3.3%): The medial and lateral parts unite to form a trunk that drains into the right inferior pulmonary vein

The medial vein typically has a diameter of approximately 4.1 ± 1.6 mm when measured at the level of the bronchus intermedius.