The right and left common iliac veins are formed by the union of the external and internal iliac veins at the level of the sacroiliac joint. They ascend to join at the level of L4-L5, to the right of the midline, forming the inferior vena cava. The right common iliac vein is short and nearly vertical. The left common iliac vein is longer and oblique, crossing beneath the right common iliac artery.
May-Thurner syndrome (iliac vein compression syndrome) occurs when the right common iliac artery compresses the left common iliac vein against the underlying vertebral column, producing chronic left-sided deep vein thrombosis and lower limb venous hypertension predominantly in young women. Endovascular stenting of the compressed left common iliac vein has become the standard treatment for symptomatic May-Thurner syndrome. The common iliac veins are at significant risk during anterior approaches to the lumbosacral spine, retroperitoneal lymph node dissection, and iliac crest bone grafting.
Chronic compression of the left common iliac vein by the right common iliac artery produces left-sided iliofemoral DVT in young women, presenting with left leg swelling, pain, and venous claudication, diagnosed by venography or CT venography and treated with thrombolysis and iliac vein stenting.
Avulsion or laceration of the common iliac vein during anterior lumbar spine surgery or retroperitoneal dissection causes life-threatening retroperitoneal haemorrhage, requiring immediate vascular surgical control and repair.
