What is Deep Vein Thrombosis?

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A thrombosis is a blood clot. A deep vein thrombosis (DVT) refers to a blood clot in the leg that does not travel to other parts of the body. Most DVTs occur in the veins in the calf, but they also can occur in the thigh and in the hip area. These blood clots usually begin in areas where the ability of the blood to clot is out of balance or where blood flow is stopped or decreased, for example when there is an injury to the blood vessel wall. Each year, up to 800,000 Americans suffer from DVT.


Early signs of a DVT are pain, swelling, warmth and redness in the area where the blood clot has formed.

Risk Factors

Age is the leading risk factor for DVT. Other factors that play a role are:

  • Recent surgery
  • Presence of a cancerous tumor (malignancy)
  • Personal history with blood clot
  • Family history of blood clots
  • Oral contraceptives
  • Hormone therapy
  • Family history
  • Pregnancy

Are you at risk for DVT? Assess your risk by taking a short online test* developed by AVF past president Joseph A. Caprini, MD.
*The American Venous Forum did not create nor endorses the test.


DVT can lead to post-thrombotic syndrome, another kind of vein blockage that interferes with blood flow. This complication, which occurs in up to two-thirds of people with DVT, causes pain, fluid build-up, change in skin color and skin ulcers.

In addition, DVT can have more serious consequences. It can lead to a blockage of an artery in a lung (pulmonary embolism), which can be life-threatening. This occurs in about 10 percent of people who have DVT.


There are several ways that doctors treat DVT.


Blood thinners (anticoagulants) are prescribed to reduce the blood's ability to clot. These medications do not treat the blood clot that exists, but they do prevent it from enlarging. The most common blood thinners are heparin, which is frequently given as a shot, and warfarin, which comes in pill form. It is important to work closely with your doctor when taking these medications to make sure that your dosage is at the correct level. A dose that is too low will not prevent additional blood clots; a dose that is too high can increase the risk of bleeding.

Another group of medications that treat blood clots are called "clot busters" (or thrombolytics). These drugs, which are given by IV, are used to break up more serious DVTs, as well as pulmonary embolism. They can cause serious bleeding. They are reserved for use when the blood clot is considered life-threatening.


Instead of using a medicine, doctors can insert a filter into a large vein in the abdomen in order to prevent a blood clot from breaking lose and traveling to the lungs.

Compression Stockings

These special stockings, cover the foot up to the knee, create pressure that help prevent the blood from pooling and clotting. They also help to prevent the swelling that DVT causes.

For further information please consult following chapters of Layman's Handbook of Venous Disorders:

Chapter 2: Risk Factors for Venous Thrombosis

Chapter 3: Clotting disorders

Chapter 6: Clinical Presentation of Venous Thrombosis "Clots": Deep Venous Thrombosis and Pulmonary Embolus

Chapter 7: Medical Treatment of Deep Vein Thrombosis and Pulmonary Embolus

Chapter 8: Surgical/Interventional Treatment of Acute Deep Vein Thrombosis

Chapter 9: Indications for Inferior Vena Cava Interruption

Chapter 13: Compression Therapy for Venous Disorders and Venous Ulceration