Retroperitoneal hematoma caused by a ruptured pelvic varix in a patient with iliac vein compression syndrome.

May-Thurner syndrome, or iliac vein compression syndrome (IVCS), is a rare but well-described entity. It refers to the formation of venous thrombus caused by compression of the left iliac vein, most commonly between the right iliac artery and lumbar vertebrae. Several variants of IVCS have been described, including unusual presenting symptoms, etiologies, and complications. The authors describe an unusual case of IVCS in which the patient presented with a left-sided retroperitoneal hematoma arising from a ruptured collateral venous varix shortly after the development of symptomatic left lower-extremity deep vein thrombosis.