Virchow in 1851 noted that iliofemoral venous thrombosis is more common on the left side. May and Thurner in 1957 described left common iliac vein intraluminal bands resulting from mechanical obstruction by the right common iliac artery. The typical patient with May-Thurner syndrome has left lower extremity pain and swelling, resulting in varicosities, phlebitis, deep venous thrombosis, venous stasis dermatitis, and pulmonary embolism. Imaging demonstrates narrowing of the caliber of the left common iliac vein as it passes between the right common iliac artery and the spine. Symptomatic patients also have evidence of collateral venous circulation.