May-Thurner syndrome
Encyclopedia
In medicine, May-Thurner syndrome is a rare condition in which blood clots, called deep venous thrombosis (DVT), occur in the iliofemoral vein due to compression of the common venous outflow tract of the left lower extremity. The specific problem is compression of the left common iliac vein
Common iliac vein
In human anatomy, the common iliac veins are formed by the external iliac veins and internal iliac veins and together, in the abdomen at the level of the fifth lumbar vertebrae, form the inferior vena cava. They drain blood from the pelvis and lower limbs....

 by the overlying right common iliac artery
Common iliac artery
The common iliac arteries are two large arteries that originate from the aortic bifurcation at the level of the fourth lumbar vertebra. They bifurcate into the external iliac artery and internal iliac artery ....

. This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots. May-Thurner syndrome is therefore more common in the left leg as the artery acutely overlaps the Left Iliac Vein. A broader disease profile known as nonthrombotic iliac vein lesions (NIVL) can involve both the right and left iliac veins as well as multiple other named venous segments.

Epidemiology and Diagnosis

It causes between two and five percent of lower-extremity venous disorders. May-Thurner Syndrome is often unrecognized; however current estimates are that this condition is three times more common in women than in men. It typically presents in the second to fourth decades of life.

It is important to consider May-Thurner Syndrome in patients who have no other obvious reason for hypercoagulability and who present with left lower extremity thrombosis. To rule out other causes for hypercoagulable state check the patient's: Antithrombin
Antithrombin
Antithrombin is a small protein molecule that inactivates several enzymes of the coagulation system. Antithrombin is a glycoprotein produced by the liver and consists of 432 amino acids. It contains three disulfide bonds and a total of four possible glycosylation sites...

, Protein C
Protein C
Protein C, also known as autoprothrombin IIA and blood coagulation factor XIV, is a zymogenic protein, the activated form of which plays an important role in regulating blood clotting, inflammation, cell death and maintaining the permeability of blood vessel walls in humans and other animals...

, Protein S
Protein S
Protein S is a vitamin K-dependent plasma glycoprotein synthesized in the endothelium. In the circulation, Protein S exists in two forms: a free form and a complex form bound to complement protein C4b. In humans, protein S is encoded by the PROS1 gene...

, Factor V Leiden
Factor V Leiden
Factor V Leiden is the name given to a variant of human factor V that causes a hypercoagulability disorder. In this disorder the Leiden variant of factor V cannot be inactivated by activated protein C. Factor V Leiden is the most common hereditary hypercoagulability disorder amongst Eurasians...

, and Prothrombin G20210A.

Venography
Venography
Venography is a procedure in which an x-ray of the veins, a venogram, is taken after a special dye is injected into the bone marrow or veins. The dye has to be injected constantly via a catheter, making it an invasive procedure...

 will demonstrate the classical syndrome.

In the broader disease profile the nonthrombotic iliac vein lesions (NIVLs) in the symptomatic ambulatory patient are usually not seen by venography. Morphologically, intravascular ultrasound (IVUS) has emerged as the best current tool in the broader sense. Functional testing such as duplex ultrasound, venous and interstitial pressure measurement and plethysmography are utilized routinely.

Mechanism

In contrast to the right common iliac vein
Common iliac vein
In human anatomy, the common iliac veins are formed by the external iliac veins and internal iliac veins and together, in the abdomen at the level of the fifth lumbar vertebrae, form the inferior vena cava. They drain blood from the pelvis and lower limbs....

, which ascends almost vertically to the inferior vena cava
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....

, the left common iliac vein takes a more transverse course. Along this course, it underlies the right common iliac artery
Common iliac artery
The common iliac arteries are two large arteries that originate from the aortic bifurcation at the level of the fourth lumbar vertebra. They bifurcate into the external iliac artery and internal iliac artery ....

, which may compress it against the lumbar spine.

In addition to compression the vein develops fibrous spurs from the effects of the chronic pulsatile compressive force from the artery. the Narrowed turbulent channel predisposes the patient to thrombosis.

This compressed, narrowed channel causes stasis of the blood, which is one element of Virchow's triad
Virchow's triad
Virchow's triad describes the three broad categories of factors that are thought to contribute to thrombosis.*Hypercoagulability*Hemodynamic changes *Endothelial injury/dysfunction...

 that precipitates deep vein thrombosis
Deep vein thrombosis
Deep vein thrombosis is the formation of a blood clot in a deep vein. Deep vein thrombosis commonly affects the leg veins or the deep veins of the pelvis. Occasionally the veins of the arm are affected...

.

Treatment

Management of the underlying defect is imperative to preventing further attacks. If the patient has extensive thrombosis, it may be prudent to consider pharmacologic and/or mechanical (also known as pharmacomechanical) thrombectomy to decrease the incidence of post-thrombotic syndrome. At the time of the thrombectomy the use of an inferior vena cava filter
Inferior vena cava filter
An inferior vena cava filter, also IVC filter or Greenfield Filter a type of vascular filter, is a medical device that is implanted by interventional radiologists or vascular surgeons into the inferior vena cava to prevent fatal pulmonary emboli .IVC filters are used in case of contraindication to...

 may be considered to prevent pulmonary embolism in these patients although filter use continues to evolve and will not correct the underlying lesion alone. Patients with May-Thurner syndrome may require an angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...

 of the iliac vein. Generally a braided stainless steel stent is used to support the area from further compression following angioplasty.

External links

  • Vascular medicine - Vascular medicine and angiology related topics for experts and laypersons.

See also

  • Chronic cerebrospinal venous insufficiency
    Chronic cerebrospinal venous insufficiency
    Chronic cerebrospinal venous insufficiency is a term developed by Italian researcher Paolo Zamboni in 2008 to describe compromised flow of blood in the veins draining the central nervous system...

     - Venous compression in the neck
  • Thoracic outlet syndrome
    Thoracic outlet syndrome
    Thoracic outlet syndrome is a syndrome involving compression at the superior thoracic outlet involving compression of a neurovascular bundle passing between the anterior scalene and middle scalene...

     - Similar compression in the shoulders.
  • Budd–Chiari syndrome - Venous compression or obstruction in the liver.
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