Common iliac vein

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Common iliac vein

The common iliac veins are two large veins in the pelvis. Each one is formed by the joining of the external iliac vein and the internal iliac vein. The left and right common iliac veins come together in the abdomen, around the level of the fifth lumbar vertebra, to form the inferior vena cava, which carries blood back to the heart.

These veins drain blood from the pelvis and lower limbs and run alongside the corresponding common iliac arteries. They receive blood from branches such as the iliolumbar veins; the left side also receives the median sacral vein.

The left common iliac vein is usually longer because it crosses to the right side of the body to join the inferior vena cava. The right common iliac vein is typically more vertical.

Sometimes, the left common iliac vein can be compressed between the right common iliac artery and the spine. This condition, May-Thurner syndrome, can cause leg swelling and increase the risk of blood clots. Repeated pulsations from arteries can irritate the vein and cause internal changes that narrow the vein or form webs, which can also contribute to problems.