What You Should Know About May–Thurner Syndrome

I recently was speaking to a vascular surgeon in my area about various venous problems patients experience that contribute to the formation of venous wounds and he mentioned the rare May–Thurner syndrome. It was a condition I had not heard of before. I briefly asked him about it and decided to do my own research. Here is what I found out.

When patients have May–Thurner syndrome, there is compression of the common venous outflow tract in the left lower extremity. This compression may cause swelling, ulcerations, pain or potentially deep vein thrombosis (DVT) in the iliofemoral vein. Other names for this condition are iliac vein compression syndrome, nonthrombotic iliac vein lesions and Cockett’s syndrome.

In 1957, May and Thurner’s discovery of vascular thickening in the left common iliac vein, where the right common iliac artery crosses and compresses it, linked the vascular anomaly of focal segmental venous fibrosis to the formation of iliofemoral DVT.¹

Treatment of May–Thurner syndrome is reserved for symptomatic cases.² When patients have iliofemoral DVT, the treatment of May–Thurner syndrome is geared toward prevention of the sequelae of veno-occlusive disease including post-thrombotic syndrome, venous claudication, venous stasis ulceration and chronic venous insufficiency arising from damage to the venous valve architecture. 

Michael Shao, MD, a vascular surgeon who practices in the Chicago area, states “the most common form is usually the left common iliac vein compression by the right common iliac artery. It is likely underdiagnosed and under-recognized.”³ This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots.

About 2 to 5 percent of all individuals suffering from vein disorders in the lower extremities have May–Thurner syndrome.² The condition is related primarily to a congenital condition, which may cause an aberration in the arrangement of the left common iliac vein and the right common iliac artery. May-Thurner syndrome may also have a traumatic etiology. The likelihood of the condition may increase with age and extreme weight gain. Dr. Shao also states that “this condition occurs in patients from ages 20s to 50s who present with idiopathic left-sided DVT. They may not have identifiable provoking risk factors. Many people may be walking around with a degree of May–Thurner but are likely asymptomatic as this can commonly be seen as an incidental finding on imaging such as computed tomography scan.”³

If the radiographic finding of May–Thurner is present but the patient is asymptomatic, generally the patient needs no treatment. However, when the finding of left common iliac vein compression by the right common iliac artery is apparent in association with a DVT, then referral for intervention with iliac vein stenting may be indicated. Treatment with anticoagulation alone will not address the underlying mechanical cause (namely mechanical compression) of the DVT at the left common iliac vein. When it comes to referral for intervention with venous stenting, treating physicians usually employ intravascular ultrasound, which can accurately measure the degree of compression by quantifying the luminal surface area of the site of compression in relation to the luminal surface area of the normal vein.

Have you seen a patient with May–Thurner syndrome in the presence of a leg ulceration?

References

1. May R, Thurner J. The cause of the predominantly sinistral occurrence of thrombosis of the pelvic veins. Angiology. 1957; 8(5):419–27.