Rare May-Thurner syndrome may explain left-leg swelling in women

By Axel Thors, DO, vascular and endovascular surgeon

thors-axel-BWP000YEUnilateral swelling of the left lower extremity can have multiple causes. May-Thurner syndrome may not be the first thing that comes to mind. But it's a diagnosis worth considering – and treating – especially for women who are obese, have had multiple pregnancies or have recently experienced pelvic trauma.

May-Thurner syndrome, also called iliac vein compression syndrome, occurs when the left common iliac vein is compressed against the spine by the right common iliac artery. In severe cases, it can compromise blood flow, cause scarring and lead to blood clot development. It occasionally causes a pulmonary embolism. The condition accounts for 2 to 5% of lower-extremity venous disorders and occurs three to five times more often in women than in men. Anecdotally, we usually see it in women ages 30 to the early 50s.

Ruling out May-Thurner

Multiple pregnancies, pelvic trauma, morbid obesity and joint replacement are among the risk factors for the syndrome. In addition, those with a history of deep vein thrombosis (DVT), venous disease or an existing hypercoagulable condition are more prone to it.

Initial evaluation of unilateral leg swelling in the primary care setting would typically involve a Doppler ultrasound study. May-Thurner can evade detection in these studies, however. They may miss respiratory variation in the blood flow, for example, and they often don't extend above the groin area, where the obstruction might originate. That's why it's important to refer potential cases to a vascular specialist.

While we would prefer to see patients before they experience a DVT, that's the precipitating event for most of our May-Thurner syndrome referrals. DVTs in patients with May-Thurner are less dangerous, because the scarring of the vein tissue makes it unlikely the clot can move upward, or the compressed vein simply blocks it. But providers should always rule out May-Thurner in a woman with unilateral swelling – typically in the left leg.

Treatment options vary

Absent a DVT, treatment focuses on symptom relief for the swelling using standard therapeutic blood thinners and compression therapy.

In the case of a DVT, our treatment usually involves catheter-directed pharmacomechanical thrombolysis to preserve the vein's long-term valve function. We often follow thrombloysis with intravascular ultrasound to investigate the scarring and measure the area of narrowing. Many patients will require balloon angioplasty and stent placement.

This combination of treatments has been shown to reduce postphlebitic syndrome, which commonly appears 4 to 5 years after a DVT incident. The condition, caused by the destruction of the valves, can result in skin changes, ulceration, swelling and pain.

Why choose The University of Kansas Health System

These kinds of treatments are only offered by higher-level medical centers. We also have seen a volume of patients with this condition, which deepens our experience and expertise. Our heart program has been nationally ranked by U.S. News & World Report among the nation's top 50 hospitals for cardiovascular care each year since 2007. Our board-certified physicians are nationally recognized for their work in developing new approaches to preventing, diagnosing and treating vascular disease. They treat many patients who have been considered too high risk by other cardiac care programs.

We welcome referrals for any concerns about the blood vessels – veins or arteries – especially if the risk factors described here apply. We will be happy to work with you to help arrive at a clear diagnosis and treatment plan for your patient.

Dr. Axel Thors, FACS, RPVI, is a vascular and endovascular surgeon at The University of Kansas Health System and an assistant professor at the University of Kansas Medical Center. He specializes in treatment and surgery for numerous vascular conditions, including abdominal aortic aneurysm, carotid occlusive disease, aortic aneurysm and peripheral artery disease. He is board-certified in surgery and vascular surgery by the American Board of Surgery.