What is May-Thurner Syndrome?

What is May-Thurner Syndrome?

May-Thurner syndrome, or STD, is a compression syndrome of the iliac vein. This is where the left common iliac vein, which carries blood from the left leg, is pressed by the right common iliac artery, which supplies the right leg with blood. The pressure occurs at a point where the artery passes through the vein and causes the vein to crush against the bones of the spine. Scarring and narrowing of the vein occurs, and symptoms of pain and swelling in the legs may be felt. Sometimes people with May-Thurner syndrome can develop blood clots in their veins, a condition known as deep vein thrombosis or DVT.

Causes and symptoms

May-Thurner syndrome is characterized by deep vein thrombosis or phlebitis (formation of a clot in the vein). This phlebitis results from compression of the left iliofemoral vein, between the right primary iliac artery and the 5th lumbar vertebra. This phenomenon can lead to pain, ulcers, edema, blood circulation and coagulation disturbances. 


Women between the ages of 20 and 50 are most likely to develop May-Thurner syndrome. In mild cases, there may be no symptoms. As the disease progresses, the left leg can become permanently swollen. With DVT, the leg may also hurt, appear red and be hot, and the veins may appear more prominent than usual. It is important to treat DVT because it can lead to a life-threatening pulmonary embolism, where the clot breaks off and blocks blood supply to the lungs.



May-Thurner syndrome usually involves doing something called a venography. A special dye, visible on x-rays, is injected into a vein in the foot and travels to the common iliac vein, where it shows blood flow through the vein. The pressure of the blood flowing to either side of the narrow section can be measured to assess the severity of the blockage.

Treatment and management

Management of May-Thurner syndrome usually involves treatment of any associated DVT and enlargement of the narrowed vein. Medicines to break a blood clot can be given directly through a narrow tube inserted into the vein. Once any clot has been treated, a surgical procedure called angioplasty may be done. This involves stretching the narrowed vein by inflating a special type of balloon inside. A mesh tube can then be inserted and left inside the vein to keep it open at all times. The basic treatment is medication (anticoagulants).

Other possible treatments include bypassing the blocked vein or moving the right iliac artery so that it no longer causes compression. Sometimes the artery is kept away from the vein with a kind of body tissue wrap. The outlook for someone with May-Thurner syndrome is generally positive if treatment is started early, before, or soon after a clot has formed.


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