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Deep vein thrombosis (throm-BO-sis), or DVT, is a blood clot that forms in a vein deep in the body. Blood clots occur when blood thickens and clumps together. Most deep vein blood clots occur in the lower leg or thigh. They also can occur in other parts of the body.
DVT affects 2 million Americans each year. This is a serious condition which is associated with fractures of the leg, pregnancy, surgery, prolonged air travel or familial disorders that increase the clotting ability of the blood. DVT is usually associated with leg pain and swelling, and the diagnosis is made with ultrasound.
Treatment consists of immediate anticoagulation (blood thinning medications) as well as other options depending on the patient's condition. DVT is dangerous because the clots can break off and travel to the lungs, causing serious complications and even death. Anyone with symptoms of a DVT (new swelling or prolonged pain in one leg) should seek immediate medical attention, particularly if they have any of the associated conditions or circumstances listed above.
A blood clot in a deep vein can break off and travel through the bloodstream. The loose clot is called an embolus. When the clot travels to the lungs and blocks blood flow, the condition is called pulmonary embolism (PULL-mun-ary EM-bo-lizm), or PE. PE is a very serious condition. It can damage the lungs and other organs in the body and cause death.
- Blood clot in the legs.
- Venous thrombosis.
- Venous thromboembolism (VTE). This term is used for both deep vein thrombosis and pulmonary embolism.
Blood clots in the thigh are more likely to break off and cause PE than blood clots in the lower leg or other parts of the body. Blood clots also can form in veins closer to the skin's surface. However, these clots won't break off and cause PE.
The animation 1 below shows a deep vein blood clot. Click the "start" button to play the animation. Written and spoken explanations are provided with each frame. Use the buttons in the lower right corner to pause, restart, or replay the animation, or use the scroll bar below the buttons to move through the frames.
Blood clots can form in your body's deep veins if:
- Damage occurs to a vein's inner lining. This damage may result from injuries caused by physical, chemical, or biological factors. Such factors include surgery, serious injury, inflammation, and an immune response.
- Blood flow is sluggish or slow. Lack of motion can cause sluggish or slow blood flow. This may occur after surgery, if you're ill and in bed for a long time, or if you're traveling for a long time.
- Your blood is thicker or more likely to clot than normal. Certain inherited conditions (such as factor V Leiden) increase blood's tendency to clot. This also is true of treatment with hormone replacement therapy or birth control pills.
The animation shows how a blood clot in a deep vein of the leg can break off, travel to the lungs, and block blood flow.
Many factors increase your risk for deep vein thrombosis (DVT). They include:
- A history of DVT.
- Disorders or factors that make your blood thicker or more likely to clot than normal. Certain inherited blood disorders (such as factor V Leiden) will do this. This also is true of treatment with hormone replacement therapy or birth control pills.
- Injury to a deep vein from surgery, a broken bone, or other trauma.
- Slow blood flow in a deep vein from lack of movement. This may occur after surgery, if you're ill and in bed for a long time, or if you're traveling for a long time.
- Pregnancy and the first 6 weeks after giving birth.
- Recent or ongoing treatment for cancer.
- A central venous catheter. This is a tube placed in a vein to allow easy access to the bloodstream for medical treatment.
- Being older than 60 (although DVT can occur at any age).
- Being overweight or obese.
Your risk for DVT increases if you have more than one of the risk factors listed above.
The signs and symptoms of deep vein thrombosis (DVT) may be related to DVT itself or to pulmonary embolism (PE). See your doctor right away if you have signs or symptoms of either condition. Both DVT and PE can cause serious, possibly life-threatening complications if not treated.
Deep Vein Thrombosis
Only about half of the people who have DVT have signs or symptoms. These signs and symptoms occur in the leg affected by the deep vein clot. They include:
- Swelling of the leg or along a vein in the leg
- Pain or tenderness in the leg, which you may feel only when standing or walking
- Increased warmth in the area of the leg that's swollen or in pain
- Red or discolored skin on the leg
Some people don't know they have DVT until they have signs or symptoms of PE. Signs and symptoms of PE include:
- Unexplained shortness of breath
- Pain with deep breathing
- Coughing up blood
Rapid breathing and a fast heart rate also may be signs of PE.
Your doctor will diagnose deep vein thrombosis (DVT) based on your medical history, a physical exam, and the results from tests. He or she will identify your risk factors and rule out other causes of your symptoms.
To learn about your medical history, your doctor may ask about:
- Your overall health
- Any prescription medicines you're taking
- Any recent surgeries or injuries you've had
- Whether you've been treated for cancer
During the physical exam, your doctor will check your legs for signs of DVT. He or she also will check your blood pressure and your heart and lungs.
Your doctor may recommend tests to find out whether you have DVT. The most common tests used to diagnose DVT are:
- Ultrasound. This is the most common test for diagnosing deep vein blood clots. Ultrasound uses sound waves to create pictures of blood flowing through the arteries and veins in the affected leg.
- A D-dimer test. This test measures a substance in the blood that's released when a blood clot dissolves. If the test shows high levels of the substance, you may have a deep vein blood clot. If your test is normal and you have few risk factors, DVT isn't likely.
- Venography (ve-NOG-ra-fee). This test is used if ultrasound doesn't provide a clear diagnosis. Dye is injected into a vein, and then an x ray is taken of the leg. The dye makes the vein visible on the x ray. The x ray will show whether blood flow is slow in the vein. This may indicate a blood clot.
Other less common tests used to diagnose DVT include magnetic resonance imaging (MRI) and computed tomography (CT) scanning. These tests provide pictures of your organs and tissues.
You may need blood tests to check whether you have an inherited blood clotting disorder that can cause DVT. This may be the case if you have repeated blood clots that can't be linked to another cause, or if you develop a blood clot in an unusual location, such as a vein in the liver, kidney, or brain.
If your doctor thinks that you have pulmonary embolism (PE), he or she may recommend more tests, such as a lung ventilation perfusion scan (VQ scan). A lung VQ scan uses a radioactive material to show how well oxygen and blood are flowing to all areas of the lungs.
For more information about tests used to diagnose PE, see the Diseases and Conditions Index Pulmonary Embolism article.
Vascular surgeons treat DVT with medications or minimally invasive procedures. Their main goals include:
- Stopping the blood clot from getting bigger
- Preventing the blood clot from breaking off and moving to your lungs
- Reducing your chance of having another blood clot
Anticoagulants (AN-te-ko-AG-u-lants) are the most common medicines for treating DVT. They're also known as blood thinners.
These medicines decrease your blood's ability to clot. They also stop existing blood clots from getting bigger. However, blood thinners can't break up blood clots that have already formed. (The body dissolves most blood clots with time.)
Blood thinners can be taken as either a pill, an injection under the skin, or through a needle or tube inserted into a vein (called intravenous, or IV, injection).
Warfarin and heparin are two blood thinners used to treat DVT. Warfarin is given in pill form. (Coumadin® is a common brand name for warfarin.) Heparin is given as an injection or through an IV tube. There are different types of heparin. Your doctor will discuss the options with you.
Your doctor may treat you with both heparin and warfarin at the same time. Heparin acts quickly. Warfarin takes 2 to 3 days before it starts to work. Once the warfarin starts to work, the heparin is stopped.
Pregnant women usually are treated with just heparin because warfarin is dangerous during pregnancy.
Treatment for DVT using blood thinners usually lasts from 3 to 6 months. The following situations may change the length of treatment.
- If your blood clot occurred after a short-term risk (for example, surgery), your treatment time may be shorter.
- If you've had blood clots before, your treatment time may be longer.
- If you have certain other illnesses, such as cancer, you may need to take blood thinners for as long as you have the illness.
The most common side effect of blood thinners is bleeding. This happens if the medicine thins your blood too much. This side effect can be life threatening.
Sometimes, the bleeding is internal (inside your body). People treated with blood thinners usually have regular blood tests to measure their blood's ability to clot. These blood tests are called PT and PTT tests.
These tests also help your doctor make sure you're taking the right amount of medicine. Call your doctor right away if you have easy bruising or bleeding. These may be signs that your medicines have thinned your blood too much.
These medicines interfere with the blood clotting process. They're used to treat blood clots in patients who can't take heparin.
These medicines are given to quickly dissolve a blood clot. They're used to treat large blood clots that cause severe symptoms.
Because thrombolytics can cause sudden bleeding, they're used only in life-threatening situations.
Vena Cava Filter
A vena cava filter is used if you can't take blood thinners or if you're taking blood thinners and still developing blood clots.
The filter is inserted inside a large vein called the vena cava. The filter catches blood clots that break off in a vein before they move to the lungs. This prevents pulmonary embolism. However, it doesn't stop new blood clots from forming.
Graduated Compression Stockings
These stockings can reduce the swelling that may occur after a blood clot has developed in your leg. Graduated compression stockings are worn on the legs from the arch of the foot to just above or below the knee.
These stockings are tight at the ankle and become looser as they go up the leg. This creates gentle pressure up the leg. The pressure keeps blood from pooling and clotting.
There are three types of compression stockings. One type is support pantyhose. These offer the least amount of pressure.
The second type is over-the-counter compression hose. These stockings give a little more pressure than support pantyhose. Over-the-counter compression hose are sold in medical supply stores and pharmacies.
Prescription-strength compression hose are the third type of compression stockings. These stockings offer the greatest amount of pressure. They also are sold in medical supply stores and pharmacies. However, you need to be fitted for them in the store by a specially trained person.
Talk with your doctor about how long you should wear compression stockings.
You can take steps to prevent deep vein thrombosis (DVT).
If you're at risk for DVT or pulmonary embolism (PE), you can help prevent the condition by:
- Seeing your doctor for regular checkups.
- Taking all medicines as your doctor prescribes.
- Getting out of bed and moving around as soon as possible after surgery or illness. This lowers your chance of developing a blood clot.
- Exercising your lower leg muscles during long trips. This helps prevent a blood clot from forming.
If you've had DVT or PE before, you can help prevent future blood clots by following the above steps and:
- Taking all medicines that your doctor prescribes to prevent or treat blood clots
- Following up with your doctor for tests and treatment
- Using compression stockings as your doctor directs to prevent swelling in your legs from DVT
Your risk of developing DVT while traveling is small. The risk increases if the travel time is longer than 4 hours or you have other DVT risk factors.
During long trips, it may help to:
- Walk up and down the aisles of the bus, train, or airplane. If traveling by car, stop about every hour and walk around.
- Move your legs and flex and stretch your feet to encourage blood flow in your calves.
- Wear loose and comfortable clothing.
- Drink plenty of fluids and avoid alcohol.
If you're at increased risk for DVT, your doctor may recommend wearing compression stockings while traveling or taking a blood-thinning medicine before traveling.
If you've had a deep vein blood clot, you're at greater risk for another one. During treatment and after, it's important to:
- Take steps to prevent deep vein thrombosis (DVT). (See "How Can Deep Vein Thrombosis Be Prevented?")
- Check your legs for signs and symptoms of DVT. These include swollen areas, pain or tenderness, increased warmth in swollen or painful areas, or red or discolored skin on the legs.
- Contact your doctor right away if you have signs or symptoms of DVT.
Ongoing Health Care Needs
Medicines that thin your blood and prevent blood clots are used to treat DVT. These medicines can thin your blood too much and cause bleeding (sometimes inside the body). This side effect can be life threatening.
Bleeding may occur in the digestive system or the brain. Signs and symptoms of bleeding in the digestive system include:
- Bright red vomit or vomit that looks like coffee grounds
- Bright red blood in your stools or black, tarry stools
- Pain in your abdomen
Signs and symptoms of bleeding in the brain include:
- Severe pain in your head
- Sudden changes in your vision
- Sudden loss of movement in your arms or legs
- Memory loss or confusion
If you have any of these signs or symptoms, get treatment right away.
- Seek treatment right away if you have a lot of bleeding after a fall or injury. This could be a sign that your DVT medicines have thinned your blood too much.
- Talk to your doctor before taking any medicines other than your DVT medicines. This includes over-the-counter medicines. Aspirin, for example, also can thin your blood. Taking two medicines that thin your blood may raise your risk of bleeding.
- Ask your doctor about how your diet affects these medicines. Foods that contain vitamin K can change how warfarin (a blood-thinning medicine used to treat DVT) works. Vitamin K is found in green, leafy vegetables and some oils, like canola and soybean oils. Your doctor can help you plan a balanced and healthy diet.
- Discuss with your doctor whether drinking alcohol will interfere with your medicines. Your doctor can tell you what amount of alcohol is safe for you.