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May Thurner Syndrome

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May Thurner syndrome, also called the iliac vein compression syndrome, is a rare medical condition that affects the left common iliac vein. The iliac vein is a large deep vein in the pelvis/lower abdomen through which blood from the leg exits. May Thurner syndrome is most commonly caused when the left iliac vein is compressed by the right iliac artery. Pressure exerted by the right iliac artery forces the left iliac vein to narrow and sometimes to scar. Such vein compression may also cause leg pain or swelling, and it increases the risk of deep vein thrombosis (DVT), a blood clot that may partially or completely block blood flow through the vein.

May Thurner syndrome is an uncommon condition with no known risk factors. However, the condition is found most commonly in young women, especially if they are taking birth control pills, or during or after pregnancy. Patients with May Thurner syndrome may be asymptomatic or may experience leg pain, swelling and/or blood clots. Many May Thurner syndrome symptoms overlap with those of deep vein thrombosis, so it is important to obtain a proper diagnosis from a physician with expertise in venous conditions before starting treatment.

Diagnostic tests commonly used to check for May Thurner syndrome include ultrasound, magnetic resonance imaging (MRI), computed tomography (CT) scan and venography.

May Thurner syndrome treatment may include:

  • Anticoagulation medication designed to thin the blood, thereby dissolving blood clots and promoting better blood flow through the left iliac vein.
  • Catheter-directed thrombolytic therapy injections designed to dissolve blood clots in the compressed veins, using a medicinal injection, a mechanical device or a combination or both techniques.
  • Combined angioplasty and stent treatments meant to stretch open a compressed vein after treatment to dissolve existing blood clots is performed. Stents may serve to prevent further narrowing of the left iliac vein in the future.

The prognosis for patients who seek medical treatment for May Thurner syndrome is generally good, especially if the compressed vein is detected early. Patients should see a doctor immediately if they notice signs of vein compression or if they think they may be experiencing symptoms of deep vein thrombosis.

May Thurner syndrome is sometimes referred to as iliocaval compression syndrome, or Cockett syndrome. For more information about blood clots and other vein conditions, contact a local vein specialist listed on DoctorQA for a consultation. A vein specialist will be able to evaluate your May Thurner syndrome symptoms and procure a proper diagnosis for you before you look at treatment options.


Reviewed by Steven E. Zimmet, MD, RVT, FACPh
Editor of Phlebology
President, Zimmet Vein & Dermatology
Past-President, American College of Phlebology

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