May-Thurner Syndrome

• The May-Thurner syndrome is the symptomatic compression of the left common iliac vein between the right common iliac artery and the lumbar vertebrae.
• In 1851, Virchow observed the sinistral (left-sided) predominance of deep venous thrombosis of the legs and proposed this explanation.
• More than a century later, May and Thurner noted the presence of venous webs, or “spurs,” in the left common iliac vein in 22% of autopsies. They attributed these spurs to scarring from repetitive compression of the common iliac vein by pulsations of the overlying common iliac artery.
• Compression of the iliac vein has been documented in approximately 50% of patients with left iliac vein thrombosis.

[Reference]
http://content.nejm.org/cgi/reprint/357/1/53.pdf