May-Thurner syndrome (also called iliac vein compression) occurs when the right iliac artery passes through the left iliac vein. Sometimes, this can cause compression of the iliac vein in that location. This anatomical change increases the chance of developing deep vein thrombosis (DVT).
Symptoms of May-Thurner Syndrome
Symptoms of May-Thurner syndrome may include pain and/or swelling, but in many cases there are no symptoms. Symptomatic May-Thurner syndrome is more common in women in their 20s and 30s. It is usually diagnosed during DVT treatment.
increased risk of blood clots
Compression of the left common iliac vein can cause irritation/injury to the vessel, resulting in thickening of the vessel wall. This thickening of the blood vessel wall causes blood to pool (also called stasis), which increases the risk of clot formation. This risk factor, along with other risk factors for blood clots, such as hormonal contraceptives (birth control pills) or the inability to walk for extended periods of time after surgery, may further increase this risk.
May-Thurner syndrome is usually diagnosed with imaging tests such as color Doppler ultrasound, computed tomography angiography, or magnetic resonance venography (intravenous MRI). Intravascular ultrasound (ultrasound that goes inside a blood vessel) is very helpful in observing compression of the left common iliac vein.
After a diagnosis of May-Thurner syndrome, tests (sometimes called “hypercoagulability tests”) are usually done to look for other risk factors for clot formation.
If blood clots are present, anticoagulation therapy is required. Unfortunately, long-term treatment with anticoagulants (blood thinners such as heparin, enoxaparin, or warfarin) is insufficient because the clot must be removed to prevent the development of post-thrombotic syndrome. Treatment with “anticoagulant” drugs such as tissue plasminogen activator (tPA) is usually required at the time of diagnosis; tPA is usually delivered directly to the clot area through a catheter.
Treating blood clots is only part of the treatment. Removing the blood clot will not treat the underlying problem of left common iliac vein compression, putting it at high risk for clot formation. To prevent further blood clots from forming, a stent — a small wire mesh — can be placed to keep the vein open. These treatments (tPA and stenting) may occur concurrently with intravascular ultrasound, allowing confirmation of the diagnosis and determination of treatment.
Anticoagulation is generally continued for several months after stent placement, but long-term may not be necessary.