Deep Vein Thrombosis
Deep vein thrombosis (throm-BO-sis) is a blood clot that forms in a vein deep in the body. Most deep vein clots occur in the lower leg or thigh. They also can occur in other parts of the body.
If a clot in a vein breaks off and travels through your bloodstream, it can lodge in your lung. This is called pulmonary embolism (PUL-mo-ner-e EM-bo-lizm), which is a very serious condition that can cause death. Blood clots in the thigh are usually more likely to break off and cause pulmonary embolism than clots in the lower leg or other parts of the body.
A blood clot also can occur in veins that are close to the surface of the skin. This type of blood clot is called superficial venous thrombosis or phlebitis (fle-BI-tis). Blood clots in superficial veins are not dangerous because they canít travel to the lungs.
The animation below shows a blood clot in deep vein thrombosis. 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.
Other Names for Deep Vein Thrombosis
Who Is At Risk for Deep Vein Thrombosis?
- Venous thrombosis
- Blood clot in the legs
Many factors may increase your risk for deep vein thrombosis:
- Having an inherited blood clotting disorder
- Having slowed blood flow, resulting from injury, surgery, or immobilization, in a deep vein
- Having cancer and undergoing treatment for it
- Having other medical conditions, such as varicose veins
- Sitting for a long period of time, for example, on a long trip in a car or on an airplane
- Pregnancy, especially the first 6 weeks after giving birth
- Being over age 60 (although deep vein thrombosis can occur in any age group)
- Being overweight
- Taking birth control pills or hormone therapy, including for postmenopausal symptoms
- Having a central venous catheter, which accounts for almost 1 in 10 cases
Your risk for deep vein clots increases if you have several risk factors at the same time. For example, a woman with an inherited condition for clotting who also takes birth control pills has an even higher risk to have a blood clot.
Signs and Symptoms
It is important to see a doctor right away if you have symptoms of deep vein thrombosis or pulmonary embolism. Deep vein thrombosis can cause very serious complications if not treated.
Deep Vein Thrombosis
Only about half of the people with deep vein thrombosis have symptoms. The symptoms may include:
- Swollen area of the leg.
- Pain or tenderness in the leg. The pain is usually in one leg and may be felt only when standing or walking.
- Increased warmth in the area of the leg that is swollen or in pain.
- Red or discolored skin.
Some people find out that they have deep vein thrombosis only after the clot has moved from the leg and traveled to the lung (pulmonary embolism). The symptoms may include:
- Chest pain when you take a deep breath
- Shortness of breath
Your doctor will obtain a medical history and examine you to determine if you have deep vein thrombosis.
Commonly Used Tests
Duplex ultrasound is the most commonly used test to diagnose deep vein clots. It uses sound waves to evaluate the flow of blood in your veins. A gel is put on the skin of the leg. A handheld device is placed on the leg and passed back and forth over the affected area. This device sends sound waves from the leg to an ultrasound machine. A computer then turns the sound waves into a picture. The picture is displayed on a TV screen where your doctor can see the blood flow in your leg.
Venography may be performed if the duplex ultrasound does not provide a clear diagnosis. A venogram is an x ray used to examine veins. A 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. If the blood flow in the vein is slowed, it will show on the x ray.
Less Frequently Used Tests
Magnetic resonance imaging (MRI) shows pictures of organs and structures inside the body. MRI uses radio waves to make the image. In many cases, MRI can provide information that would not show up on an x ray. This test is being used more frequently to diagnose deep vein thrombosis.
Computed tomography scan is a special type of x ray that can provide pictures of structures inside the body. This test is rarely used to diagnose deep vein thrombosis.
If an inherited blood clotting disorder is suspected, tests may be run for it. The presence of an inherited clotting disorder is suggested by:
- Repeated blood clots that canít be linked to any other cause
- Development of a blood clot in a vein at an unusual location, such as a vein in the liver, kidney, or brain
The main goals in treating deep vein thrombosis are to:
- Stop the clot from getting bigger
- Prevent the clot from breaking off in your vein and moving to your lungs
- Reduce your chance of having another blood clot
Several types of medicine may be used to treat and/or prevent deep vein thrombosis:
Anticoagulants decrease your blood's ability to clot. They are also known as blood thinners. They are used to stop clots from forming in people who are at risk for clots and to stop already formed clots from getting bigger. They do not break up blood clots that have already formed. (The body itself dissolves most clots over time.)
Anticoagulants can be taken as either a pill (warfarin) or an injection (heparin).
Treatment for deep vein thrombosis with anticoagulants usually lasts from 3 to 6 months. However, the following situations may change the length of treatment:
- If your blood clot occurred after a short-term risk (for example, surgery), your treatment may be shorter.
- If you have had clots before, you will need longer treatment.
- If you have certain other illnesses, such as cancer, you may need to take anticoagulants for as long as the illness is present.
The most common side effect of anticoagulants is bleeding. You should call your doctor right away if you are taking warfarin or heparin and have easy bruising or bleeding. Blood tests can check how well the medicine is working.
Thrombolytics are medicines given to quickly dissolve a blood clot. They are used to treat large clots that cause severe symptoms. Because thrombolytics can cause sudden bleeding, they are used only in life-threatening situations.
Thrombin inhibitors are medicines that interfere with the clotting process. They are used to treat some types of clots and for patients who canít take heparin.
Vena cava filters are used when you canít take medicines to thin your blood, or when you are taking blood thinners but continue to develop clots anyway. The filter is inserted inside a large vein called the vena cava. The filter catches clots that break off in a vein before they move through the bloodstream to the lungs (pulmonary embolism). The filter doesnít prevent new clots from developing.
Graduated compression stockings can reduce the chronic swelling that can occur after a blood clot has developed in a leg. The leg swelling is due to damage to the valves in the leg veins. 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 causes a gentle compression (or pressure) up the leg. The pressure keeps blood from pooling and clotting.
Some drawbacks of wearing the stockings are:
- They can be uncomfortable when worn all day.
- They can be hot.
- They may be difficult to put on, especially for older adults and overweight people.
Preventing deep vein thrombosis depends on whether you have had a clot before and on your risk factors for developing a clot.
If you have had a deep vein clot before, future clots may be prevented by:
- Taking the medicines prescribed by your doctor to prevent or treat blood clots
- Following up with your doctor for medicine changes and blood tests
If you have never had a deep vein clot but have risks factors for developing one, you may be able to prevent a clot by:
- Exercising your lower leg muscles, if you will be sitting still for long periods of time.
- Getting out of bed and moving around as soon as you are able to after a long period of being bedridden, such as after having surgery or being ill. The sooner you move around, the less chance you have of developing a clot.
- Taking the medicines prescribed by your doctor to prevent or treat blood clots after some types of surgery.
- Following up with your doctor.