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May-Thurner syndrome (MTS), is also known as the iliac vein compression syndrome.
It is a condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or deep venous thrombosis in the iliofemoral veins.
The syndrome is due to left common iliac vein compression by the overlying right common iliac artery.
It is associated with compression on the left common iliac vein between the right common iliac artery and the vertebrae, resulting in venous congestion in the development of DVT.
It is thought to represent between two and five percent of lower-extremity venous disorders.
The compression leads to stasis of blood, which predisposes to the formation of blood clots.
Typically manifest and young women after surgery or peripartum.
Clinical manifestations include:
pain when the limb is dependent and/or significant swelling of the limb.
The right common iliac vein, which ascends almost vertically to the inferior vena cava.
The left common iliac vein traverses diagonally from left to right to enter the inferior vena cava.
The left common iliac vein traverses under the right common iliac artery, which may compress it against the lumbar spine and limit the flow of blood out of the left leg.
The left iliac vein is frequently seen to be compressed in asymptomatic patients, and considered an anatomic variant- a 50% luminal compression of the left iliac vein occurs in a quarter of healthy individuals.
If this compression becomes clinically hemodynamically significant does it cause changes in venous flow or venous pressure, or if it leads to acute or chronic DVT.
Along with compression, the vein develops intraluminal fibrous from the chronic pulsatile compressive force from the artery.
The narrowed compromised vein turbulence predisposes the patient to thrombosis, often causes collateral blood vessels to form.
Collateral veins connect both internal iliac veins, thus creating outflow through the right common iliac vein.
The compressed, narrowed outflow channel causes stasis of the blood,
that precipitates deep vein thrombosis.
May-Thurner syndrome is considered in patients who have no other obvious reason for hypercoagulability and who present with left lower extremity thrombosis.
Venography will demonstrate the classical syndrome when causing deep venous thrombosis.
Ultrasound is the best tool in diagnosis.
Compression of the left common iliac vein may be seen on pelvic CT.
Diagnosis needs to be confirmed with imaging: magnetic resonance venography, venogram and usually confirmed with intravascular ultrasound because the flattened vein may not be noticed on conventional venography.
Uncomplicated cases may be managed with compression stockings.
Severe May-Thurner syndrome may require thrombolysis if there is a recent onset of thrombosis, followed by angioplasty and stenting of the iliac vein.
A stent may be used to support the area from further compression following angioplasty.
Usually there is not a thrombotic component in these cases, but it may occur at any time.
The condition is three times more common in women than in men.
The syndrome typically presents in the second to fourth decades of life.
It becomes symptomatic following trauma, or a change in functional status such as swelling following orthopaedic joint replacement.