May-Thurner Syndrome (MTS), also called iliac vein compression syndrome, is a vascular condition that affects blood flow in the legs. It occurs when the right iliac artery in the pelvic region compresses the left iliac vein against the lower spine. This compression can impair blood flow from the leg back to the heart, increasing the risk of deep vein thrombosis (DVT).

Although only 2% to 3% of the population is formally diagnosed with MTS, up to 22% may unknowingly have the condition due to its often silent nature. It primarily affects people assigned female at birth between the ages of 20 and 50. When symptoms do arise, they typically include a dull ache, swelling, or heaviness in the affected leg.

Symptoms

Many individuals with MTS do not exhibit symptoms unless a blood clot develops. If symptoms occur, they are usually present in the left leg and may include swelling, a feeling of heaviness or fullness, aching, tenderness, throbbing pain, varicose veins in the upper leg, skin discoloration, ulcers, lower back pain, or chronic pelvic pain.

Symptoms of Deep Vein Thrombosis

When MTS leads to a blood clot, symptoms such as leg swelling, cramp-like pain, red or purple skin discoloration, and warmth to the touch may occur. These symptoms often indicate a serious progression of the syndrome.

Causes

MTS results from the compression of the left iliac vein by the right iliac artery, which narrows the vein and restricts blood flow. While the exact cause is unclear, anatomical differences in pelvic blood vessels, sometimes present from birth or developing over time due to factors like pregnancy, are thought to contribute.

Risk Factors

Certain factors can increase the likelihood of developing MTS, including being assigned female at birth, being between the ages of 20 to 50, pregnancy, use of oral contraceptives, recent surgery, and dehydration. MTS also raises the risk of blood clots in the affected leg.

Diagnosis

Diagnosis involves evaluating medical history, physical symptoms, and performing diagnostic tests. Providers look for signs such as leg swelling, varicose veins, discoloration, and warmth. Common diagnostic tools include venous duplex ultrasound, MDCT venography, MRV imaging, and D-dimer blood tests.

Stages of May-Thurner Syndrome

  • Stage 1: Compression of the left iliac vein without damage or symptoms.

  • Stage 2: Fibrous tissue forms in the vein wall, possibly limiting blood flow but often without symptoms.

  • Stage 3: Severe compression causes DVT, swelling, and varicose veins.

Treatment Options

The aim of treatment is to restore proper blood flow, relieve symptoms, and prevent clot formation. For those without clots, angioplasty and stenting are common. This procedure involves using a catheter and balloon to widen the vein, followed by stent placement.

In cases involving DVT, treatment may include anticoagulants to prevent clots, thrombolytic drugs to dissolve existing clots, and vena cava filters to prevent clots from reaching the lungs.

Compression Therapy

Wearing compression socks may help in early stages by promoting blood flow and preventing clots. These socks gently squeeze the legs to support circulation.

Prevention Tips

While MTS cannot always be prevented, risk can be minimized through regular physical activity, avoiding prolonged sitting or standing, staying hydrated, maintaining a healthy weight, quitting smoking, and eating a balanced diet.

Associated Conditions

People with MTS are more prone to deep vein thrombosis, chronic venous insufficiency, pulmonary embolism, and post-thrombotic syndrome. These conditions can arise when blood flow is significantly impaired.

Living With MTS

Most people with MTS lead normal lives with appropriate treatment and lifestyle changes. Staying active, eating well, wearing compression stockings, and following medical advice can help prevent complications and improve quality of life. If symptoms change or worsen, consulting a healthcare provider is essential.