Definition Venous thrombosis is the formation of a blood clot in a vein. Deep venous thrombosis (DVT) means that a blood clot has formed in one of the large veins that are far below the skin.
What is going on in the body? DVT is most common in the legs, but it can occur in other parts of the body. A blood clot in a vein blocks the normal flow of blood back to the heart. It also causes the affected vein to become inflamed. DVT can occur for many reasons.
What are the signs and symptoms of the condition? The symptoms of DVT include:
pain, usually in the calf or thigh
swelling, usually in one leg
warm, reddened skin, usually in the calf or thigh, that is tender to the touch
a "rope" or cord that can be felt in the vein along the course of the blood clot
What are the causes and risks of the condition? Some of the causes of DVT are:
surgery, especially in the pelvis or abdomen
prolonged lack of activity, such as long-term bed rest or long periods of sitting in a car or plane
increased thickness of the blood, called a hypercoagulable state. This can occur for many reasons, including an inherited tendency to form blood clots.
A person who has already had a blood clot has an increased risk of having another one.
The most serious risk of DVT is a pulmonary embolism. This is a piece of the blood clot that breaks off and travels to the lung. A blood clot in the lung can cause death. DVT may also cause chronic pain and swelling of the affected leg.
What can be done to prevent the condition? Avoiding long periods of inactivity can reduce the risk of DVT. This is especially important for people who have a history of DVT. For example, it's good to start to walk soon after surgery. On long trips, it's important to take breaks to stretch or walk.
There are also medications that can help prevent DVT. These include heparin, exonaparin, and warfarin. Compression stockings can also be used to help prevent DVT.
How is the condition diagnosed? The medical history and a physical examination play an important role in diagnosing DVT. DVT is suspected when a person has swelling of one leg, pain in the calf or thigh, and recent surgery, trauma, or prolonged inactivity. Doppler, a type of ultrasound, is commonly used to diagnose DVT. Other types of x-ray tests may also be used in some cases.
What are the long-term effects of the condition? Most patients will recover from an episode of DVT without long-term problems. People who have had DVT have a higher risk of getting it again. DVT increases the risk of a pulmonary embolism, which can be fatal. There are rare cases of a stroke resulting from a DVT. Chronic swelling and pain of the affected leg may also occur.
What are the risks to others? DVT is not contagious and poses no risk to others. Women who smoke are advised not to take the combined oral contraceptive pill for fear of thrombosis.
What are the treatments for the condition? The main purpose of treatment is to prevent a blood clot in the lung. Bed rest and elevating the leg can help reduce the swelling and pain. The person is often given an injection of a medication to thin the blood. The injection may be given through an IV or under the skin. These blood-thinning medications, such as heparin and exonaparin, help prevent further growth of the blood clot. The person is closely monitored to make sure they are stable. After a few days of blood thinner injections, the person can be switched to pills. Warfarin is the most common blood thinning pill, or anticoagulant.
In some people, blood thinners cannot be used for various reasons. For example, a person may have a high risk of bleeding, a side effect of thinning the blood. In these cases, a surgical procedure can be done. This involves inserting a filter in one of the major veins of the body that leads to the heart. This filter catches any clots that break off so they cannot get into the lungs and cause death.
What are the side effects of the treatments? Heparin can cause bleeding and lower blood platelet counts, called thrombocytopenia. Warfarin can also cause bleeding, which in rare cases is fatal. Warfarin interferes with many other drugs.
What happens after treatment for the condition? Most patients with DVT will recover fully. When DVT is in the pelvis or upper leg, warfarin is usually taken for at least 3 to 6 months. DVT in the veins of the calf is usually treated with warfarin for at least 6 weeks. In people who develop a second DVT, warfarin treatment is continued for life. This long-term therapy is also used in people with underlying causes of DVT, such as cancer or "thick" blood.
How is the condition monitored? People with a history of DVT must avoid prolonged periods of immobility. They also need to watch for the common symptoms of leg pain and swelling. For those on warfarin, the International Normalized Ratio (INR) blood test helps monitor the effectiveness of the blood-thinning therapy.
Author: Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 23/11/2004 Contributors Potential conflict of interest information for reviewers available on request
