Deep Venous Thrombosis (DVT)


Deep venous thrombosis (DVT) refers to the formation of a blood clot in the deep venous system, a network of large veins with extensive branching that covers the whole body.

The most common site for deep venous thrombosis is in the deep veins of the legs and thighs. This is, in part, explained by the “pooling” of blood in a person’s leg veins due to gravity, especially during periods of prolonged immobilisation such as long distance travelling, hospitalisation or after major surgery. For this reason, the condition is sometimes known as the “economy-class syndrome”

Why Have I Developed a DVT?

Risk Factors

Any one may be at risk for DVT, but the presence of the following risk factors can increase one’s chance of developing DVT.

  • Hospitalisation for a medical illness
  • Recent major surgery or injury
  • Previous history of DVT
  • Known personal history or a family history of a clotting disorder
  • History of active cancer and concurrent cancer therapy
  • Pregnancy and first 6 weeks after delivery
  • Smoking
  • Hormone replacement therapy or high dose combined oral contraceptive pill
  • Being overweight or obese
  • Prolonged sitting (greater than 6 to 8 hours)

Sometimes people develop blood clots for no apparent reason. These are often called spontaneous DVT

What are the Symptoms and Signs of a DVT?

Pain and swelling are usually the main symptoms of a DVT. Sometimes the area around a blood clot can feel warmer than the surrounding tissues.

Deep Venous thrombosis and Pulmonary Embolus

DVT isolated in the leg veins can result in pain, skin inflammation and ulceration. However, if the clot breaks off and travels through the bloodstream into the lungs, it can seriously affect lung and heart functions. This condition is known as pulmonary embolus (PE). PE can be life-threatening and may result in death.

Diagnosis of DVT: How are blood clots detected?

The diagnosis of DVT based on symptoms alone can be difficult. A venous doppler ultrasound is frequently ordered to confirm the diagnosis. Ultrasound machines use sound waves to detect blood flow in veins and arteries. A clot can be detected because of the decreased blood flow in the veins. Ultrasound is painless and does not have any major side effects. Sometimes blood tests are also used to help in the detection of blood clots.

Doppler Ultrasound demonstrating presence of a DVT

Ultrasound evaluation demonstrates the presence of a blood clot (deep vein thrombosis) in the leg. On the left, the vein (arrow) is compressed with the ultrasound probe and would normally collapse, however remains patent. On the right, the pressure is released and the same vein (arrow) containing the clot is more obvious.
[*Image courtesy Melbourne Radiology Clinic]

What are the main problems with DVT's?

There are three main problems with a blood clot in the deep veins.

1The first problem is that blood clots in the deep veins can be painful and cause lots of swelling. A number of medications can be used to treat the pain and it is important to limit the swelling as much as possible. The best way to decrease swelling is to use tight (graduated compression) stockings. These stockings are very tight at the ankle and less tight in the calf and so they help the blood return "uphill" to the heart. These stockings are very tight at the ankle and less tight in the calf and so they help the blood return "uphill" to the heart. It is also important to keep your leg up (elevated) as much as possible. (See the related information sheet on Graduated Compression Stockings).

2The second problem is that blood clots can sometimes break off and travel to the lungs and seriously affect lung and heart functions. This condition is known as pulmonary embolus (PE). PE can be life-threatening and may result in death.

3The third problem of blood clots is that once a vein is blocked with a clot, other veins will need to take over the role of the blocked vein. Sometimes this can cause long term swelling of the leg which can be uncomfortable and lead to skin changes including ulcers (this is called Post Thrombotic Syndrome or PTS).

What is the Treatment of DVT?

Most treatment for DVT can occur without hospitalisation – this may be necessary however if there are extensive clots or there is a suspicion of pulmonary embolus. Blood thinning (anticoagulation) is the main treatment for DVT and PE to prevent further blood clots. They can be in the form of an injection (e.g. Clexane) or tablets (e.g. warfarin).

In very serious cases, a medication to dissolve the blood clot can be used. There is a significant risk of bleeding with this medication and you should discuss this carefully with your doctor. This will require close monitoring in a hospital.

What Can I Do to Prevent Further DVT?

Maintaining a healthy lifestyle is important to reduce the risk of further DVT. This includes:

  • quit smoking
  • maintain ideal body weight
  • regular exercise
  • maintain adequate hydration and legs movement, especially during long distance travel
  • selective use of compression stockings and low dose anticoagulant drugs in high-risk hospitalised patients.

For related information: Read the Fact Sheets:
Below Knee DVT - Calf vein thrombosis (Distal deep vein thrombosis (DVT)
Pulmonary Embolus (PE)


  1. Vascular Disease Foundation (
  2. Better Health Channel (
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