Common iliac vein

The left and right common iliac veins come together in the abdomen at the level of the fifth lumbar vertebra,[1] forming the inferior vena cava.

[3] The vena cava is to the right of the midline and therefore the left common iliac vein is longer than the right.

[2] Overlying arterial structures may cause compression of the upper part of the left common iliac vein.

The resulting intraluminal elastin and collagen deposition can cause intimal fibrosis and the formation of venous spurs and webs.

This can lead to narrowing of the vein and cause persistent unilateral leg swelling, contributing to venous thromboembolism.