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What Causes Deep Vein Thrombosis in the Leg?

H. Colledge
H. Colledge

Deep vein thrombosis, sometimes known as deep venous thrombosis or DVT, is a potentially serious condition in which a clot of blood, or thrombus, develops inside a vein. Most often, this occurs in the leg inside what is called a deep vein, which passes through a muscle in the thigh or calf. Anything which slows the flow of blood in the circulation, such as long air or road journeys or periods of illness where a person is confined to bed, can increase the likelihood of a deep vein thrombosis in the leg. Deep vein thromboses are also at risk to form if the walls of blood vessels are damaged by conditions such as injury or infection. Sometimes factors such as smoking or taking certain drugs alter the composition of the blood and increase its tendency to clot, making a deep vein thrombosis in the leg more likely.

When a person is inactive for long periods, the muscles in the leg, which would normally contract and help to keep blood moving, remain idle. This can lead to slower blood flow inside the deep veins that run through the muscles. A deep vein thrombosis in the leg could then result, causing symptoms of swelling, pain, warmth and redness. The condition is usually treated using anticoagulant drugs and compression stockings. If left untreated, there is a risk that a piece of the clot could break off and travel to the lungs, resulting in an inability to breathe which could be fatal.

Deep vein thrombosis develops when a blood clot forms inside a vessel of the leg.
Deep vein thrombosis develops when a blood clot forms inside a vessel of the leg.

Inactivity is the most common cause of a deep vein thrombosis in the leg. This could be the result of an illness such as a broken leg or a condition requiring treatment in intensive care, where someone is unable to move for a length of time. Long journeys may require that the legs remain in an immobile and cramped state, and it is important to move about as much as possible when traveling. Sometimes a surgical operation could take several hours to perform, increasing the chance that a venous clot might form. Being pregnant or overweight increases the pressure on blood in the legs and raises the risk of DVT occurring, and a failing heart can also lead to blood pooling in the lower limbs.

Compression stockings may be prescribed in addition to an anti-coagulant to treat deep vein thrombosis.
Compression stockings may be prescribed in addition to an anti-coagulant to treat deep vein thrombosis.

The wall of a vein may be injured by factors such as inflammation, and there is then a higher chance of clots developing at the damage site. Inflammation could be the result of cancer or other diseases, an infection, exposure to chemicals, or drugs such as those used in chemotherapy. Vein walls may also be injured by medical procedures, illegal drug use, or by a previously existing clot. Smoking, old age, hormone treatments and some medical conditions can increase the tendency for a clot, occasionally leading to deep vein thrombosis in the leg.

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    • Deep vein thrombosis develops when a blood clot forms inside a vessel of the leg.
      By: ras-slava
      Deep vein thrombosis develops when a blood clot forms inside a vessel of the leg.
    • Compression stockings may be prescribed in addition to an anti-coagulant to treat deep vein thrombosis.
      By: nito
      Compression stockings may be prescribed in addition to an anti-coagulant to treat deep vein thrombosis.
    • Compression stockings can reduce the risk of getting blood clots in the lower legs by supporting blood circulation of the limbs.
      By: Andreja Donko
      Compression stockings can reduce the risk of getting blood clots in the lower legs by supporting blood circulation of the limbs.