Deep vein thrombosis (DVT) is a blood clot (thrombus) in a deep vein, usually in the legs.
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.footnote 1
What causes deep vein clots to form?
Blood clots 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.
What are the symptoms?
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 become constant.
If a blood clot is small, it may not cause symptoms. In some cases, pulmonary embolism is the first sign that you have DVT.
How is deep vein thrombosis diagnosed?
If your doctor suspects that you have DVT, you probably will have an ultrasound test to measure the blood flow through your veins and help find any clots that might be blocking the flow.
How is it treated?
Treatment lowers the chance that the blood clot will grow or that a piece of the clot might break loose and flow to your lungs.
Treatment for DVT usually involves taking blood thinners (anticoagulants) for at least 3 months to prevent existing clots from growing.
Your doctor also may recommend that you prop up or elevate your leg when possible, take walks, and wear compression stockings. These measures may help reduce the pain and swelling that can happen with DVT.
How can deep vein thrombosis be prevented?
There are things you can do to prevent DVT. After surgery, you can take an anticoagulant medicine to prevent blood clots. You might also wear compression stockings. You can try to get up and out of bed as soon as possible after an illness or surgery. If you are sitting for a long time, like during a long flight, you can exercise your legs to help blood flow.
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Deep vein thrombosis (DVT) is a blood clot in a deep vein, usually in the legs. Things that lead to a blood clot in a vein include:
Slowed blood flow, which can happen when you're not active for long periods of time.
Abnormal clotting problems, which make the blood clot too easily or too quickly.
Injury to the blood vessels, because blood is more likely to clot in veins shortly after they are injured.
Symptoms
Deep vein thrombosis often does not cause symptoms or causes only minor symptoms. When symptoms occur, they include:
Swelling.
Warmth.
Pain or tenderness. The pain may be in the calf or thigh and may be present only when the affected area is touched or when standing or walking.
Redness.
Other problems may cause symptoms like those of DVT. So diagnosing DVT can be difficult. These problems include less serious problems like cellulitis or a pulled muscle.
Symptoms of pulmonary embolism
Sometimes life-threatening pulmonary embolism is the first sign that you have DVT. Pulmonary embolism is the sudden blockage of an artery in the lung. Symptoms of pulmonary embolism include:
Sudden shortness of breath.
Chest pain that may get worse with a deep breath.
A cough that may bring up blood.
A fast heart rate.
Fainting.
What Happens
Pulmonary embolism
When you have deep vein thrombosis (DVT), the main goal of treatment is to prevent the blood clot from growing or moving to the lungs. If a blood clot breaks loose, it can travel to the lungs and block blood flow (pulmonary embolism). A pulmonary embolism is an emergency. Treatment for DVT lowers your risk for this problem.
The risk of a pulmonary embolism can depend on the location of the blood clot. A pulmonary embolism is more likely if a blood clot is at or above the knee than if it is in the calf. But a blood clot in a calf also has a chance of causing a pulmonary embolism.
After the first time you have deep vein thrombosis, there is a risk of having blood clots again. Your risk can depend on what caused your blood clot and how it was treated. Your doctor will treat you to try to prevent blood clots from happening again.
Post-thrombotic syndrome
If you have had DVT, you have a risk of a painful complication called post-thrombotic syndrome. Anticoagulant medicine may help lower the risk of this complication.
What Increases Your Risk
Many things increase your risk for deep vein thrombosis (DVT). These include:
When you first see the doctor, he or she will do a physical exam and ask questions about your medical history. These help your doctor decide what tests you need based on your risk for deep vein thrombosis (DVT).
Physical exam
Your doctor will check:
Your heart and lungs.
Your legs for warmth, swelling, bulging veins, or changes in skin color.
Medical history
Your doctor may ask:
Do you have any swelling or pain in your legs?
Have you had a blood clot before?
What medicines do you take?
Have you had surgery recently or have you been on any long trips lately?
Ultrasound test
Ultrasound is the main test used to help diagnose DVT. It creates a picture of the flow of blood through the veins.
If your doctor thinks you should have more tests, you might have two or three more ultrasounds over the next 2 weeks.
Additional tests
More tests may be used when ultrasound results are unclear. These tests often aren't needed, but they may help diagnose or exclude a blood clot in the leg. These tests may include:
If your doctor thinks you might have a pulmonary embolism, he or she may test your lungs. For more information, see the topic Pulmonary Embolism.
Blood thinner testing
If you are treated with anticoagulant medicines, you may need periodic blood tests to monitor the effects of the anticoagulant on the blood. Blood tests include:
Prothrombin time (PT), also referred to as INR, to monitor treatment with warfarin (Coumadin).
Tests for clotting problems
Special blood tests may help identify inherited blood-clotting problems that can increase your risk of forming blood clots or help explain why you got a blood clot. These tests check for genetic conditions or specific proteins in your blood.
Testing might be done if you have or had one or more of the following:
A blood clot in a vein that has no clear cause
A blood clot at age 45 or younger
A blood clot in a vein at an unusual location, such as the gastrointestinal region, the brain, or the arms
A first-degree family member (mother, father, brother, or sister) who has had a blood clot in a vein before age 45 or has had problems with blood clotting
Screening for these problems in the general population is not routinely done.
Treatment Overview
The main goals of treatment for deep vein thrombosis (DVT) are:
To prevent the blood clot from becoming larger.
To prevent the blood clot from traveling to the lungs (pulmonary embolism).
To prevent post-thrombotic syndrome, a condition that can cause pain, sores, and swelling of the affected leg.
To prevent blood clots from returning.
Medicine
DVT is usually treated with anticoagulant medicines. These medicines are often called blood thinners, but they do not actually thin the blood. They prevent blood clots by increasing the time it takes a blood clot to form. Also, anticoagulants help prevent existing blood clots from becoming larger.
You might take anticoagulants for at least 3 months. The length of time will vary based on your own health, where the blood clot is in your leg, and your risk for a pulmonary embolism.footnote 2
Other treatments may be used in the hospital for some people. These treatments include thrombolytic medicine or vena cava filters. These treatments are not common. They might be used for people who are at risk for serious problems from DVT.
Preventive measures might be used before and after any procedure or event that increases your risk of deep vein thrombosis (DVT). These measures include:
Taking anticoagulants to prevent a blood clot that can form after some types of surgery.
Quitting smoking to lower your risk of blood clots.
Exercising your lower leg muscles to improve circulation in your legs. Point your toes up toward your head so that the calves of your legs are stretched, then relax. Repeat. This exercise is especially important to do when you are sitting for long periods of time.
Getting up out of bed as soon as possible after an illness or surgery. It is very important to get moving as soon as you are able. If you cannot get out of bed, do the leg exercise described above every hour to keep the blood moving through your legs.
Sitting still for a long flight or road trip raises your risk of getting blood clots. It's important to take steps to prevent blood clots when you travel, such as getting up and moving around every hour or so on a long flight.
In the hospital
Intermittent pneumatic compression (IPC) devices are also used to prevent DVT. These devices inflate and deflate knee-high boots, which reduces pooling of blood in the legs. IPC pumps are often used when people stay in a hospital.
Home Treatment
Home treatment for deep vein thrombosis (DVT) focuses on:
Taking anticoagulants (blood thinners) safely.
Relieving symptoms.
Wearing compression stockings.
Taking anticoagulants safely
If you take an anticoagulant medicine, also called a blood thinner, you need to take extra steps to avoid bleeding problems. These steps include:
Preventing falls and injuries.
Telling your doctors about all other medicines, supplements, and vitamins that you take.
Getting regular blood tests, if your doctor tells you to.
To relieve symptoms like pain and swelling, your doctor might recommend:
Walking 5 or 6 times a day, if possible.
Elevating your leg.
Wearing compression stockings.
If you are not taking an anticoagulant, your doctor might suggest that you take a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen, to relieve pain. Do not take an NSAID unless your doctor tells you that it's safe for you.
Wearing compression stockings
Compression stockings are specially fitted stockings. They are tightest at the foot. They get less and less tight farther up on your leg.
For treatment, you might take anticoagulants for at least 3 months. The length of time will be based on your own health, the location of the blood clot in your leg, and your risk for a pulmonary embolism.footnote 2
In the hospital, you might be given an anticoagulant as a shot or through an IV. After you go home, you might give yourself shots for a few days. For long-term treatment, you'll likely take a pill.
Thrombolytic medicines are not commonly used to treat DVT. Although they can quickly dissolve a blood clot, thrombolytics also greatly increase the risk of serious bleeding. They might be used for people who are at risk for serious problems from DVT.
How long will you need medicine?
If you're taking anticoagulants after surgery to prevent DVT, you only need the medicine for a short time. This might be 2 weeks or more, depending on the medicine and the type of surgery you had.
For treatment of deep vein thrombosis, you will likely take an anticoagulant for at least three months. You might take it longer, depending on your health.
You might take anticoagulants for a long time, maybe the rest of your life, if you:
Have had blood clots before or have cancer or other risk factors that make it likely you'll get another blood clot.
Surgery to remove a blood clot is rare. It's only considered if the blood clot is very large and is blocking a major blood vessel. Surgery increases the risk of forming new blood clots.
Other Treatment
Vena cava filters are used for some people who have deep vein thrombosis. For example, vena cava filters may be used if a person cannot take anticoagulant medicine. This is not a common treatment.
A vena cava filter is inserted into the vena cava, the large vein that returns blood to the heart from the abdomen and legs.
This filter can prevent blood clots from traveling to the lungs (pulmonary embolism). But the filter doesn't stop a clot from forming.
References
Citations
U.S. Department of Health and Human Services (2008). The Surgeon General's call to action to prevent deep vein thrombosis and pulmonary embolism. Available online: http://www.surgeongeneral.gov/library/calls/deepvein/index.html.
Guyatt GH, et al. (2012). Executive summary: Antithrombotic therapy and prevention of thrombosis, 9th ed.-American College of Chest Physicians evidence-based clinical practice guidelines. Chest, 141(2, Suppl): 7S-47S.
Credits
ByHealthwise Staff Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine Adam Husney, MD - Family Medicine Kathleen Romito, MD - Family Medicine Jeffrey S. Ginsberg, MD, FRCPC - Hematology
U.S. Department of Health and Human Services (2008). The Surgeon General's call to action to prevent deep vein thrombosis and pulmonary embolism. Available online: http://www.surgeongeneral.gov/library/calls/deepvein/index.html.
Guyatt GH, et al. (2012). Executive summary: Antithrombotic therapy and prevention of thrombosis, 9th ed.-American College of Chest Physicians evidence-based clinical practice guidelines. Chest, 141(2, Suppl): 7S-47S.
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