What Is May-Thurner Syndrome?
Medically reviewed by Oluseun Olufade, MD
May-Thurner syndrome is a mechanical problem of blood flow in the legs that can increase your chances of having a blood clot. This problem occurs when your right iliac artery compresses your left iliac vein. It is also called iliac vein compression syndrome or Cockett's syndrome.
May-Thurner syndrome affects two blood vessels that travel to your legs. It causes pressure and abnormal blood flow. This can lead to severe results.
Since symptoms do not always occur with this syndrome, you can have it and not know it. Having May-Thurner syndrome raises your risk of deep vein thrombosis (DVT), a clotting problem that can become severe and threaten your life. Treatment is used when a blood clot occurs.
This article describes May-Thurner syndrome symptoms, causes, diagnosis, treatment, and outlook.
How Does May-Thurner Syndrome Affect the Body?
May-Thurner syndrome is a vascular compression disorder. It affects your arteries (blood vessels that carry oxygen-rich blood from your heart to other areas of your body) and veins (blood vessels that collect oxygen-poor blood and return it to your heart).
May-Thurner syndrome is caused when your right iliac artery compresses your left iliac vein. As this pressure increases, it prevents blood from flowing normally through your legs and back to your heart. It also increases your risk of DVT (a blood clot—thrombus—in a deep vein) at the site where your iliac vein is pinched.
May-Thurner syndrome is a progressive disease that develops through three stages:
Stage 1: Asymptomatic compression of the left iliac vein
Stage 2: Formation of a spur (projection or lesion) in the iliac vein
Stage 3: Occurrence of DVT in your left iliac vein
What Causes May-Thurner Syndrome?
May-Thurner syndrome is caused when your left iliac vein is compressed by your right iliac artery. This is a relatively common, occurring in as much as one-third of the population. It is not an inherited or genetic condition, and it is unclear what causes this to happen.
Having the following characteristics are risk factors for symptomatic May-Thurner syndrome:
Female sex
Second to fourth decade of life
History of oral contraceptive use
Recent pregnancy or postpartum state
Prolonged immobilization
Hypovolemia (decreased volume of circulating blood in your body)
May-Thurner Syndrome Symptoms
Early signs of May-Thurner syndrome can include symptoms of altered venous flow in your legs. These include the following characteristics, which typically occur in your left leg:
Swelling, fullness, or heaviness in your leg or foot
Venous ulcers or sores that do not heal on your leg
Varicose veins in your leg
Many people don’t experience symptoms of May-Thurner syndrome until it results in a DVT. When DVT occurs, it is usually in your left leg and involves the following symptoms:
Pain or tenderness typically described as a cramp or charley horse
Swelling and burning
Red or purple skin color
Skin that feels warm to the touch
When to Seek Emergency Care for a Blood Clot
With May-Thurner syndrome, it is possible for a piece of a DVT to break off and travel to your lung, causing a pulmonary embolism (blood clot in your lungs). This is a medical emergency. Seek immediate medical attention or call 911 if you have any of the following symptoms:
Shortness of breath or difficulty breathing
Chest pain, especially when you are trying to take a breath
Passing out or fainting
How Is May-Thurner Syndrome Diagnosed?
There are no standardized criteria for the diagnosis of May-Thurner syndrome. A diagnosis begins with a complete physical evaluation, including medical history and discussion of symptom duration and severity.
Based on the findings of your clinical examination, your healthcare provider may use one or more of the following May-Thurner syndrome radiology tests:
Color Doppler ultrasound: This produces a two-dimensional (2D) image of your blood vessels to show your blood vessel structure, clot location, and blood flow. It is typically the initial test used to determine venous insufficiency because it is noninvasive, easy to perform, accessible, safe, and cost-effective.
Magnetic resonance venography (MRV): Magnetic resonance venography uses magnets, radio waves, and specialized computers to create 2D and three-dimensional (3D) images of your blood vessels. MRV can provide detailed views of obstructions with little risk of harm.
Computed tomography venography (CTV): Computed tomography venography is a type of X-ray that provides detailed pictures of the inside of your body to identify damage from a pulmonary embolism or other blood clot.
Computed tomography angiography (CTA): This produces a CT scan with an injection of a special dye. It shows pictures of blood vessels and tissues to differentiate between thrombotic and non-thrombotic obstructions.
Intravascular ultrasound: This uses sound waves to see inside blood vessels to evaluate blood flow. The procedure uses a tiny ultrasound attached to the top of a catheter (thin tube). The catheter is inserted into an artery in your groin and moved up to your heart where it measures sound waves reflected off blood vessels and changes those sound waves into pictures.
Contrast venography: Contrast venography is an X-ray that uses an injection of contrast material to show how blood flows through your veins. It can help determine whether a blockage is a blood clot or another type of problem.
Learn More: How Blood Clots Are Diagnosed
May-Thurner Syndrome Treatment
Treatment for May-Thurner syndrome focuses on keeping your veins open and preventing blood clots. Since there is no consensus or formalized guideline for the management of May-Thurner syndrome treatment, a wide range of options are used. Treatment for this syndrome includes the following:
Angioplasty and stenting: This procedure starts with angioplasty, which involves the insertion of a catheter with a balloon into the left iliac vein. The balloon is inflated to open the vein. It is followed by stenting, which involves the insertion of a stent (a small mesh tube) into the opened vein to keep it open and prevent the backflow of blood.
Bypass surgery: Vascular bypass surgery restores normal blood flow interrupted in the iliac vein. It uses a small piece of donor tissue or tissue from another part of your body to reroute the blood flow around the compressed portion of the iliac vein.
Surgery to reposition the right iliac artery: This procedure involves repositioning the right iliac artery to relieve compression on the left iliac vein. A section of tissue may be used to decrease the pressure between the vein and artery.
When DVT occurs with May-Thurner syndrome, your healthcare provider may advise one of the following treatments:
Blood thinners: Blood thinners (anticoagulants) are recommended as a first-line treatment for acute DVT or pulmonary embolism.
Clot-buster medications: Clot-busting medications are provided via thrombolysis, a catheter-based procedure that delivers the medicine directly to the site of the blood clot.
Vena cava filter: This filter stops blood clots that form in the veins of the lower half of your body. It helps to prevent a potential pulmonary embolism when blood thinners are not effective or can't be used.
Complications Associated With May-Thurner Syndrome
While many people do not have symptoms of May-Thurner syndrome, it is possible to develop complications that can become life-threatening. These complications include the following:
Leg swelling
Chronic venous insufficiency (a condition in which blood pools in your veins causing swelling, pressure, skin changes, venous ulcers, or sores that don't heal)
DVT
Chest pain
Coughing up a mixture of blood and mucus
The blood clot breaking off and traveling to your lungs, heart, or brain, increasing the risk of pulmonary embolism, heart attack, stroke
What Is Postsurgical Recovery Like?
Recovery from surgery for May-Thurner syndrome varies depending on the type of procedure performed and your overall condition.
Surgery is often performed on an outpatient basis. While your procedure may be performed in a hospital, it is likely that you will be discharged the same day to recover at home.
It is typical to be advised to rest for four to five days before returning to regular activities. Your progress and blood flow will be monitored with follow-up visits beginning about one week after your procedure, continuing at regular intervals for the first year after surgery. Treatment with blood thinners may be needed after surgery to prevent the recurrence of a blood clot.
Learn More: Recovering From Surgery
May-Thurner Syndrome Life Expectancy
May-Thurner syndrome life expectancy can be normal for most people. In the majority of cases, the condition remains asymptomatic. Most people with May-Thurner syndrome live a long life and never know they have it. However, when May-Thurner syndrome causes DVT, it can quickly become a life-threatening event at any time.
Tips for Living With May-Thurner Syndrome
Living with May-Thurner syndrome involves making healthy choices to reduce your risk of DVT. The following can help keep venous circulation properly flowing:
Engage in regular aerobic exercise.
Quit smoking and avoid the use of any type of tobacco.
Discuss your risks of DVT when choosing birth control or hormone replacement therapy.
Break up prolonged periods of immobilization, such as long car rides by getting up and walking every one to two hours.
Exercise your legs while sitting for long periods of time.
Wear graduated compression stockings.
Take anticoagulants as advised by your healthcare provider.
Wear loose-fitting clothes.
Maintain a healthy weight.
Avoid a sedentary lifestyle.
When to Seek Emergency Care
If DVT breaks off and forms a clot in your lungs, you may notice the following symptoms that require immediate emergency care:
Chest pain that’s worse when you breathe in
Coughing up blood
A faster heartbeat than normal
Passing out
Shortness of breath
Other breathing problems
Excessive sweating
Bluish lips or nails
Summary
May-Thurner syndrome occurs when your right iliac artery exerts pressure on your left iliac vein. The effect raises your risk of deep vein thrombosis. This is a blood clot deep in your iliac vein that can threaten your life.
It becomes a problem more often in females between the ages of 20 and 40. While there is no known cause, those who have had pregnancies or long periods of inactivity have the highest risk.
While you can have this syndrome without symptoms, any sign of this disease should be checked promptly. Treatment of symptoms can reduce your risk of DVT.
