May-Thurner Syndrome

May-Thurner Syndrome (MTS), also known as iliac vein compression syndrome, is a condition where there is compression of the left iliac vein by the right iliac artery in the pelvis. This compression impairs the flow of blood through the left iliac vein, which can lead to deep vein thrombosis (DVT) in the left leg and other complications. There are different variants of MTS, depending on which pelvic artery compresses the central pelvic vein.

🔹 Anatomy and Mechanism

In May-Thurner Syndrome, the right iliac artery crosses over and compresses the left iliac vein against the lumbar spine, causing venous outflow obstruction. This impairs blood flow from the left leg back to the heart, leading to blood pooling in the left leg, and increasing the likelihood of blood clot formation (DVT).

🔸 Causes and Risk Factors

While May-Thurner Syndrome is typically a congenital (present from birth) anatomical condition, several factors can increase the risk or severity of complications associated with it:

• Female gender: MTS is more common in women, especially in younger individuals.
• Pregnancy: As the uterus expands, it can increase pressure on the iliac veins and worsen compression.
• Obesity: Excess weight can exacerbate the pressure on the veins.
• Prolonged immobility: Conditions such as long periods of sitting (e.g., long flights) or bed rest can increase the risk of clot formation.
• History of DVT or clotting disorders: If a person has a history of blood clots, they may be more likely to develop MTS or experience complications like DVT.
• Genetic predisposition to clotting disorders: Conditions such as Factor V Leiden or antithrombin III deficiency can increase clotting tendencies.

🔹 Symptoms of May-Thurner Syndrome

May-Thurner Syndrome can often remain asymptomatic, but when symptoms occur, they may include:

1. Pain, swelling, or heaviness in the left leg: Often worsened after standing or prolonged sitting.
2. Deep Vein Thrombosis (DVT): The compression of the left iliac vein can lead to blood clot formation, causing symptoms like swelling, redness, and pain in the left leg.
3. Skin changes: Chronic swelling and poor blood flow may cause skin discoloration or ulcers, particularly near the ankle.
4. Fatigue or discomfort: A general feeling of heaviness or fatigue in the affected leg.
5. Varicose veins: Enlarged veins that may be visible under the skin of the left leg.

🔸 Diagnosis of May-Thurner Syndrome

Diagnosing MTS involves several steps:

1. Physical Examination: The doctor may look for signs of swelling, tenderness, and any visible varicose veins in the affected leg. A history of previous blood clots or chronic leg discomfort may also be assessed.
2. Duplex Ultrasound: The most common and non-invasive diagnostic tool used to evaluate blood flow and detect DVT in the veins.
3. CT Venography or MRI: These imaging techniques can provide a detailed view of the veins and arteries, showing the compression of the left iliac vein by the right iliac artery.
4. Venogram: A venogram, which is an X-ray of the veins after injecting a contrast dye, may be used to visualize the compression and assess its severity.
5. Intravascular Ultrasound: The gold standard is to place an intravascular ultrasound catheter inside the vein and look for extrinsic compression.

🔹 Treatment for May-Thurner Syndrome

Treatment for MTS focuses on improving blood flow, preventing clot formation, and relieving symptoms. Treatment options include:

1. Anticoagulation (Blood Thinners)

• Blood thinners like heparin, warfarin, or newer direct oral anticoagulants (DOACs) (e.g., apixaban, rivaroxaban) are prescribed to prevent blood clots from forming or growing. They may be used during acute treatment or long-term management.

2. Endovenous Stenting

• Stenting involves the placement of a stent (a small mesh tube) in the left iliac vein to relieve the compression caused by the right iliac artery. This is a minimally invasive procedure that helps restore proper blood flow through the vein. This is done in selected patients who have had an extensive DVT [blood clot] involving the iliac vein [in the abdomen/pelvic] or present with chronic venous insufficiency related to post thrombotic syndrome [swelling, ache, lower extremity fatigue and ulcers].

3. Thrombectomy or Thrombolysis

• If a DVT has already developed, the clot may need to be removed surgically (thrombectomy) or dissolved with a clot-busting drug (thrombolysis). This procedure is usually performed in an emergency or when the DVT is severe.

4. Compression Therapy

• Wearing compression stockings can help reduce swelling, alleviate pain, and improve circulation, especially for people with chronic symptoms.

5. Lifestyle Modifications

• Exercise: Regular walking or other leg exercises can improve circulation and reduce the risk of clots.
• Leg elevation: Elevating the left leg above the level of the heart can help reduce swelling and promote venous return.
• Weight management: Maintaining a healthy weight can help reduce pressure on the veins and improve blood flow.

6. Surgical Treatment

• In rare cases, surgical intervention may be required if the compression is severe and other treatments do not provide relief. The surgery may involve bypass surgery or the removal of excess tissue.

🔹 Complications of May-Thurner Syndrome

If untreated, May-Thurner Syndrome can lead to serious complications, including:

1. Deep Vein Thrombosis (DVT): Compression of the left iliac vein increases the risk of clot formation in the leg.
2. Pulmonary Embolism (PE): If a clot from the left leg breaks loose and travels to the lungs, it can cause a pulmonary embolism, which is a life-threatening condition.
3. Post-thrombotic Syndrome (PTS): A long-term complication after DVT, characterized by chronic pain, swelling, and skin changes in the affected leg.
4. Chronic Venous Insufficiency (CVI): The compression may lead to long-term poor circulation in the leg, causing chronic swelling and venous ulcers.

🔹 Prevention of May-Thurner Syndrome Complications

Prevention focuses on avoiding blood clots and improving circulation:

1. Exercise regularly: Physical activity, especially walking, helps promote healthy blood flow.
2. Compression stockings: Help reduce swelling and improve circulation.
3. Avoid prolonged immobility: Take breaks to move around if sitting or lying down for long periods.
4. Medication: If you have risk factors (like a history of DVT), anticoagulation therapy may be prescribed to reduce the risk of clot formation.

🔸 Prognosis

With treatment, most people with May-Thurner Syndrome can manage the condition and prevent complications like DVT and pulmonary embolism. Stenting and anticoagulation therapy have proven to be effective in improving symptoms and preventing clot formation. Regular monitoring and adherence to prescribed treatment plans are essential for maintaining good health and preventing complications.