When You Cannot Go With the Flow: A Case Report of May-Thurner Syndrome.

INTRODUCTION:May-Thurner syndrome (MTS) is caused by extrinsic compression of the left iliac venous system, most commonly between an overlying right iliac artery and fifth lumbar vertebra, and is seen mainly in women between 20 and 50 years of age. This compression may be asymptomatic but can lead to the formation of venous thrombi causing left lower extremity pain and swelling. CASE PRESENTATION:We report a case of MTS in a patient who initially presented with back and left lower extremity pain and swelling whose initial duplex venous ultrasound was negative for deep venous thrombus. Subsequent computed tomography (CT) revealed a venous thrombus of the left common, internal, and external iliac veins. DISCUSSION:In the case of unilateral lower extremity swelling with a negative initial duplex venous ultrasound, consider further investigation with CT venography to evaluate for possible MTS.