Learning About May-Thurner Syndrome

May-Thurner syndrome is a condition that affects blood flow in the pelvis and legs.

Normally, blood from your legs travels back to your heart through large veins. In May-Thurner syndrome, this blood flow is partly blocked. This happens when the left iliac vein is squeezed between an artery and a bone in the lower spine. This pressure can make the vein narrower and make it harder for blood to flow from the left leg. When blood flow slows down, pressure can build in the leg. This may lead to pain and swelling. In some cases, it can also lead to deep vein thrombosis (DVT), which is a blood clot in a deep vein.

May-Thurner syndrome is also called iliac vein compression syndrome, iliocaval venous compression syndrome, and Cockett syndrome.

May-Thurner syndrome happens when the right iliac artery crosses over and presses on the left iliac vein. It is not clear why this happens in some people.

Over time, the artery’s natural pulsing can irritate the vein wall. This can lead to:

• Damage to the vein wall.
• Thickening of the vein lining.
• Areas of scar tissue called venous spurs.
• Gradual narrowing of the inside of the vein.

When the vein becomes narrow, blood may move more slowly through it. Slow blood flow can increase the risk of a DVT.

Some people have no symptoms. This is more common when the vein is only slightly narrowed. When symptoms do happen, they usually affect the left leg.

Common symptoms include:

• Swelling in the leg.
• Leg pain or tenderness.
• A feeling of heaviness or tiredness in the leg.
• Changes in skin color (hyperpigmentation).
• Varicose veins.

Other symptoms may include:

• Leg pain during exercise that gets better with rest or after raising your leg.
• Chronic venous insufficiency. The leg veins have trouble sending blood back to the heart, and blood pools in the veins.
• Repeated blood clots in veins near the skin.
• In severe cases, open sores on the leg called venous ulcers.

Symptoms often feel worse later in the day or after sitting or standing for a long time.

May-Thurner syndrome also can cause female pelvic congestion syndrome, which can cause pelvic pain and enlarged veins.

Many people have May-Thurner syndrome without knowing it. But some people are more likely to have symptoms.

You may be at higher risk of symptoms if you:

• Are biologically female, especially if you are 20 to 40 years of age.
• Are pregnant or have recently given birth.
• Take birth control pills or hormone therapy.
• Have a condition known to increase blood clotting.
• Have a spine problem, such as scoliosis.

Other factors that may raise the risk include:

• Dehydration.
• Long periods of not moving.
• A past history of blood clots.

Diagnosis usually begins with an exam. If you have swelling in one leg or a blood clot with no clear cause, your doctor may recommend imaging tests.

One common imaging test that doctors use is duplex ultrasound. This checks blood flow and looks for blood clots. If more detail is needed, you may have either computed tomography (CT) venography or magnetic resonance (MR) venography. These scans show where the vein is compressed and how narrow it has become.

The most accurate test is intravascular ultrasound (IVUS). A small tube called a catheter is placed into the vein. It has a tiny ultrasound probe that lets doctors see the inside of the vein and measure how narrow it is.

Sometimes doctors also perform catheter venography. In this test, a catheter and a special dye are used to see the veins on an X-ray. This helps doctors measure pressure in the vein and check for blockages.

Treatment depends on your symptoms and whether you have a blood clot. If symptoms are mild, your doctor may suggest lifestyle changes such as:

• Staying active and walking often.
• Staying at a weight that's healthy for you.
• Avoiding long periods of sitting or standing.
• Staying hydrated.

Wearing compression stockings may also help blood flow better in the legs.

Other treatments include:

• Blood-thinning medicine.
• Procedures that break up or remove the clot, such as catheter-directed thrombolysis or pharmacomechanical thrombolysis.

Doctors may also treat the narrowed vein with minimally invasive procedures. These may include:

• Balloon angioplasty. This widens the vein.
• A venous stent. This is a small metal tube placed inside the vein to keep it open and help with blood flow.

After treatment, you may need to wear compression stockings or take medicine to help prevent new blood clots.

Surgery is rarely needed, but it may be used if other treatments don't work.

The most common problem (complication) of May-Thurner syndrome is deep vein thrombosis (DVT). This is a blood clot that forms in the affected leg.

In rare cases, a part of the clot can travel to the lungs. This is called a pulmonary embolism, which can be life-threatening.

Other long-term complications may include:

• Ongoing swelling in the leg.
• Chronic venous insufficiency. The leg veins can't move blood back to the heart easily, and blood collects in the veins.
• Changes in skin color.
• Skin breakdown or ulcers on the lower leg.

Many people with May-Thurner syndrome can live healthy lives, especially when the condition is diagnosed and treated.

Self-care may include:

• Lifestyle changes, such as walking regularly and staying at a weight that is healthy for you.
• Wearing compression stockings.
• Watching for possible blood clots.
• Taking blood-thinning medicine if your doctor recommends it.

Procedures such as venous stenting can also help improve blood flow and reduce symptoms.

If you have had a blood clot, your doctor may suggest regular checkups to help prevent future clots or other problems.

Working with your doctor and following your treatment plan can help support healthy blood flow, control symptoms, and improve your quality of life.