Magnetic resonance venography in the diagnosis and management of May-Thurner syndrome.

Isolated left lower extremity swelling secondary to left iliac vein compression was first described by McMurrich in 1908, and defined anatomically by May and Thurner in 1957 and clinically by Cockett and Thomas in 1965. The left iliac vein is usually located posterior to the right iliac artery and can be compressed between the artery and the fifth lumbar vertebrae. Symptoms include left lower extremity edema, pain, varicosities, venous stasis changes, and deep venous thrombosis. Evaluation of these patients historically included a venous duplex scan to rule out deep venous thrombosis and an abdominal computed tomography scan to rule out pelvic mass. This paper describes the use of magnetic resonance imaging and venography in the evaluation of patients with isolated left lower extremity swelling. A retrospective analysis of a series of 24 patients who presented with symptomatic left lower extremity edema was performed. Infrainguinal deep venous thrombosis and valvular reflux was evaluated by duplex scan. The presence of suprainguinal deep venous thrombosis and pelvic mass was evaluated by magnetic resonance imaging. Magnetic resonance imaging was used to define the anatomic characteristics of the May-Thurner syndrome. Patients identified with the syndrome were treated either conservatively with lower extremity compression and elevation or with angioplasty and stenting. Follow-up of this subset of patients was performed with clinical assessment of the resolution of their symptomatic lower extremity edema as well as quality of life assessments via phone interviews. Twenty-four patients were evaluated for isolated left lower extremity swelling. Seven patients had positive results on duplex scans for deep venous thrombosis. Magnetic resonance imaging results demonstrated 1/24 (4%) had a pelvic mass compressing the iliac vein; 2/24 (8%) patients had iliac vein thrombosis; 1/24 (4%) patients with a history of deep venous thrombosis demonstrated a long stenotic segment of the left iliac vein unrelated to its association with the right iliac artery; 9/24 patients (37%) had anatomic evidence of May-Thurner syndrome; and 2/24 patients (8%) had isolated left lower extremity swelling of unknown etiology. Five patients diagnosed with May-Thurner syndrome were treated conservatively with compression stockings and leg elevation. Four patients with May-Thurner syndrome underwent iliac vein angioplasty and stenting. Technical success was 100%. On clinical follow-up, the patients with May-Thurner syndrome have had improvement/resolution of their symptoms. There have been no complications from either therapy. May-Thurner syndrome is a clinical entity of left iliac vein compression by the right iliac artery, resulting in isolated left lower extremity swelling and may be a precipitating factor for iliofemoral deep venous thrombosis. Magnetic resonance imaging is the best modality for diagnosis of this entity as it can rule out the presence of pelvic masses and deep venous thrombosis while simultaneously demonstrating the anatomy characteristic of this syndrome.