Deep venous thrombosis Health Article

Definition

Deep venous thrombosis is a condition in which a blood clot forms in a vein that is deep inside the body.

Alternative Names

DVT; Blood clot in the legs; Thromboembolism

Causes, incidence, and risk factors

Deep venous thrombosis (DVT) mainly affects the large veins in the lower leg and thigh. The clot can block blood flow. If the clot breaks off and moves through the bloodstream, it can get stuck in the brain, lungs, heart, or other area, leading to severe damage.

Risks for DVT include:

• Bedrest
• Cigarette smoking
• Fractures
• Giving birth within the last 6 months
• Medications such as estrogen and birth control pills
• Obesity
• Recent surgery (especially hip, knee, or female reproductive organ surgery)
• Sitting for a long time, such as on a long plane or car trip

You're also more likely to develop DVT if you have any of the following conditions:

• Blood that is more likely to clot (hypercoagulability)
• Cancer
• Overproduction of red blood cells in bone marrow (polycythemia vera) or related conditions

DVTs are most common in adults over age 60, but can occur at any age.

Symptoms

• Changes in skin color (redness) in one leg
• Increased warmth in one leg
• Leg pain in one leg
• Leg tenderness in one leg
• Swelling (edema) of one leg

Signs and tests

Your health care provider will perform a physical exam. The exam may show a red, swollen, or tender leg.

The following tests may be done:

• Doppler ultrasound exam of a limb
• D-dimer blood test
• Plethysmography of the legs
• X-rays to show veins in the legs (leg venography)

Blood tests may be done to check if there is increased blood clotting. Such tests include:

• Activated protein C resistance (checks for the Factor V Leiden mutation)
• Antithrombin III levels
• Genetic testing to look for mutations that make you more likely to develop blood clots, including the prothrombin G20210A mutation
• Lupus anticoagulant or antiphospholipid antibodies
• Protein C and protein S levels
• Screening for disseminated intravascular coagulation (DIC)

This list is not all-inclusive.