In human anatomy, the common iliac veins are formed by the external iliac veins and internal iliac veins. The left and right common iliac veins come together in the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

at the level of the

fifth lumbar vertebra The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse ...

, forming the

inferior vena cava The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of th ...

. They drain

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

from the pelvis and lower limbs. Both common iliac veins are accompanied along their course by common iliac arteries.

Structure

The external iliac vein and internal iliac vein unite in front of the sacroiliac joint to form the common iliac veins. Both common iliac veins ascend to form the inferior vena cava behind the right common iliac artery at the level of the fifth lumbar vertebra. The vena cava is to the right of the midline and therefore the left common iliac vein is longer than the right. The left common iliac vein occasionally travels upwards to the left of the

aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes o ...

to the level of the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

, where it receives the left

renal vein The renal veins are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney. Because the inferior vena cava is on the right half of the body, the left renal vein is lo ...

and crosses in front of the aorta to join the inferior vena cava. The right common iliac vein is virtually vertical and lies behind and then lateral to its artery. Each common iliac vein receives

iliolumbar vein The iliolumbar vein is the vena comitans of the iliolumbar artery. The obturator nerve The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves in the lumbar plexus; the branch from ...

s, while the left also receives the

median sacral vein The median sacral vein (or middle sacral veins) is a vein of the abdomen. It accompanies the median sacral artery along the front of the sacrum. It ends in the left common iliac vein. Sometimes, it ends in the angle of junction of the two common ...

which lies on the right of the corresponding artery.

Clinical significance

Overlying arterial structures may cause compression of the upper part of the left common iliac vein. Compression of the left common iliac vein against the fifth lumbar vertebral body by the right common iliac artery as the artery crosses in front of it traditionally happens in

May–Thurner syndrome May–Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is a condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or clots (deep venous thrombo ...

. Continuous pulsation of the common iliac artery may trigger an

inflammatory response Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecu ...

within the common iliac vein. The resulting intraluminal elastin and collagen deposition can cause intimal

fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...

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 Venous thrombosis is blockage of a vein caused by a thrombus (blood clot). A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to ...

References

{{Authority control Veins of the torso Angiology Anatomy Veins