Deep Vein Thrombosis

Basic Facts

Deep vein thrombosis is a blood clot in one of the main deep veins that returns blood from a lower extremity (and less commonly, from an upper extremity) to the heart and lungs. DVT occurs when normal blood clotting is disrupted by trauma or injury, restricted mobility, cancer, major surgery, pregnancy, or a clotting disorder.
The most serious complication of deep vein thrombosis is pulmonary embolism, a life-threatening condition that occurs when a clot in the leg dislodges and travels to the heart and lungs.
The symptoms of deep vein thrombosis can be difficult to recognize, but once diagnosed, the condition is highly treatable with drug therapy, mechanical devices, or both.

Deep vein thrombosis (DVT) refers to the development of blood clots in deep veins, usually in the pelvis, thigh, and calf, which return blood to the heart and lungs. These clots occur when the body’s blood clotting system becomes unbalanced.

Many people who experience DVT never have another episode. Others have recurrent clotting episodes. One complication of DVT, post-thrombotic syndrome, causes swelling, tenderness, and pain. More dangerously, deep vein thrombosis can result in a pulmonary embolism, in which a clot breaks free and lodges in the lungs, obstructing blood flow and causing heart and lung collapse. A large pulmonary embolism can cause death within hours.


About half of all DVT cases do not cause symptoms. When symptoms are present, they may include:

  • Swelling;
  • Leg pain that may increase with walking, standing, or exertion;
  • Tenderness or warmth in the leg; and
  • Bluish or reddish discoloration of the skin.


Many factors cause clots in the body’s deep veins. They include:

  • Surgery and recovery from surgery;
  • Trauma, such as fractures;
  • Injury to the vein lining;
  • Inherited blood clotting abnormalities; and
  • Prolonged immobility (such as during long airplane flights).

Most people who develop DVT are older than 50. Besides age, risk factors may include:

  • Being overweight;
  • Lengthy surgeries or procedures involving catheters (thin tubes inserted in blood vessels);
  • Chronic diseases;
  • Pregnancy;
  • Medications; and
  • Air travel.


Symptoms of DVT are common to many unrelated conditions, and mild symptoms can sometimes mask extensive clotting. For these reasons, a suspicion of DVT must be confirmed with some form of testing. Tests include:

  • Doppler ultrasound;
  • Plethysmography (a blood pressure cuff measures changes in the blood volume of an extremity); and
  • Venography (a contrast dye is injected into the veins and x rays are taken).


Physicians seek to treat the existing clot as well as prevent pulmonary embolism and further clotting episodes. They may recommend a combination of drugs and surgical procedures, including:

  • Anticoagulants;
  • Drugs to break up clots or dissolve clots;
  • Percutaneous thrombectomy; and
  • Surgical venous thrombectomy.

If drug therapy carries too high a risk or if it proves unsuccessful, a metal filter can protect patients from embolism. The filter is inserted into the vena cava, the large abdominal vein that returns blood to the heart and lungs, and filters any breakaway leg clot before it reaches the lungs.

Because DVT is a known complication following many types of surgery, doctors often recommend that surgery patients take measures to prevent DVT, including anticoagulant therapy, compression stockings, and specialized exercises.