Deep venous thrombosis (DVT) affects mainly the veins in the lower leg and the thigh. It involves the formation of a clot (thrombus) in the larger veins of the area. This thrombus may interfere with circulation of the area, and it may break off and travel through the blood stream (embolize). The embolus thus created can lodge in the brain, lungs, heart, or other area, causing severe damage to that organ.

Risks include prolonged sitting, bedrest or immobilization (such as on long plane or car trips), recent surgery or trauma (especially hip, knee or gynecological surgery), fractures, childbirth within the last 6 months and the use of medications such as estrogen and birth control pills. Risks also include a history of polycythemia vera, malignant tumor, and inherited or acquired hypercoagulability (changes in the levels of blood clotting factors making the blood more likely to clot).

Deep venous thrombosis is more commonly seen in adults over age 60 but can occur in any age group.

• leg pain in one leg only
• leg tenderness in one leg only
• swelling (edema) of only one leg
• increased warmth of one leg
• changes in skin color of one leg, redness

An examination may reveal a red, swollen, or tender leg.

The presence of deep venous thrombosis may be seen on:

• venography of the legs
• Doppler ultrasound exam of an extremity
• plethysmography of the legs
• D-dimer blood test

• antithrombin III, protein C, protein S
• Factor V Leyden
• Prothrombin 20210a mutation
• DIC screening
• lupus anticoagulant and anticardiolipin antibodies

Treatment of DVT is intended to prevent the development of a pulmonary embolus and to prevent recurrent DVT.

For years the standard treatment has been an anticoagulant medication called heparin which was given through the vein. This results in relatively immediate anticoagulation and treatment of the clot. Along with heparin an oral medication called warfarin is given. Because warfarin usually takes several days to reach effectiveness (until it reaches a therapeutic level), the heparin is continued until the warfarin is therapeutic for at least 24 hours. The warfarin is usually continued for approximately six months though there is some debate about the optimal duration of therapy. In almost all circumstances warfarin should not be initiated until heparin has been started.

Because heparin is given as a continuous intravenous infusion, it requires hospitalization. However, newer forms of heparin, known as low molecular weight heparin (usually enoxaparin) can be used in some circumstances. This heparin can be given by injection once or twice a day and thus can shorten or eliminate the need for hospitalization.

Warfarin causes an increase in a blood clotting time known as the PT. The PT is monitored to determine if the blood is sufficiently anticoagulated. A measurement known as the INR standardizes PT measurements between labs. For most patients warfarin is adjusted to keep the INR between 2 and 3.

• pulmonary embolus
• post-phlebitic syndrome