Deep vein thrombosis
(DVT) is a
blood clot (thrombus) in a deep vein, usually in the
Clots can form in
superficial veins and in
deep veins. Blood clots with inflammation in
superficial veins (called superficial thrombophlebitis or phlebitis) rarely
cause serious problems. But clots in deep veins (deep vein thrombosis) require
immediate medical care.
These clots are dangerous because they can break
loose, travel through the bloodstream to the lungs, and block blood flow in the
lungs (pulmonary embolism). Pulmonary embolism is often
life-threatening. DVT can also lead to long-lasting problems. DVT may damage
the vein and cause the leg to ache, swell, and change color.
Blood clots most often form in the calf and thigh veins, and less often in the arm veins or pelvic
veins. This topic focuses on blood clots in the deep veins of the legs , but
diagnosis and treatment of DVT in other parts of the body are similar.
Each year in the United States, between 350,000 and 600,000 people get a blood clot in the legs or in the lungs.1
can form in veins when you are inactive. For example, clots can form if you are
paralyzed or bedridden or must sit while on a long flight or car trip. Surgery
or an injury can damage your blood vessels and cause a clot to form. Cancer can
also cause DVT. Some people have blood that clots too easily,
a problem that may run in families.
Symptoms of DVT include
swelling of the affected leg. Also, the leg may feel warm and look redder than
the other leg. The calf or thigh may ache or feel tender when you touch or
squeeze it or when you stand or move. Pain may get worse and last longer or
If a blood clot is small, it may not cause
symptoms. In some cases, pulmonary embolism is the first sign that you have