Deep vein thrombosis (DVT) is a blood clot or thrombus in a deep vein. These blood clots are most common in the leg. But they may occur in the arm or other part of the body. Part of a clot, called an embolus, can break off and travel to the lungs. This is a serious condition called pulmonary embolus (PE). A PE can cut off blood flow to all or part of the lung. PE is an emergency and may cause death.

Health care providers use the term venous thromboembolism (VTE) to describe these two conditions: DVT and PE. They use the term VTE because the two conditions are very closely related. And because their prevention and treatment are also closely related.

The deep veins of the legs are located in the muscles. These help carry blood from the legs to the heart. When leg muscles contract and relax, blood is squeezed through the veins back to the heart. One-way valves inside the veins help keep the blood moving in the right direction. When blood moves too slowly, it can collect (pool) in the veins. This makes a clot more likely to form.

Anyone can develop a blood clot. But certain factors may raise your risk for one. Anything that slows blood flow, causes injuries to the lining of a vein, or causes increases in blood clotting can make you more likely to have DVT. You are at risk for DVT if you:

• Have extra weight or obesity.
• Have a blood-clotting disorder.
• Are older than age 60.
• Had surgery.
• Have spent a long period of time not moving, such as staying in the hospital or traveling on a long trip.
• Take birth control pills or hormone replacement therapy.
• Are paralyzed.
• Are pregnant.
• Smoke.
• Have a central venous catheter (for example, in a large vein in the chest).

You are also at higher risk if you have certain diseases and conditions, such as:

• A previous blood clot.
• Varicose veins.
• Heart problems, such as heart failure or heart attack.
• Inflammatory bowel disease.
• Lupus, an autoimmune system disease.
• Cancer and some cancer treatments.

DVT may happen without symptoms. When symptoms do happen, they may be sudden. They may appear around the site of the DVT, such as the calf or thigh. You may have these common symptoms:

• Pain, especially deep in the muscle
• Swelling (edema)
• Soreness or aching
• Redness and warmth in the leg, arm, or other area
• Low-grade fever

These symptoms may mean that you have a blood clot. The symptoms of a blood clot may also look like other health problems. Always see your doctor for a diagnosis.

Your doctor will ask about your health history and do a physical exam. You may also need these other tests:

• Duplex ultrasound. This procedure involves placing ultrasound gel on the affected area and then moving a handheld device across it. A picture of the blood flow is displayed on a screen. Duplex ultrasound is the most common test for DVT.
• Blood tests. Blood tests may be done to look for blood clotting and other problems.
• Contrast venography. A venogram is a test that lets your doctor see the veins in your body, especially in your legs. A special dye is injected that can be seen on an X-ray. The dye lets your doctor check the health of your veins. This test may be used to diagnose DVT in the veins of the pelvis.

Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

The goals of treatment are:

• To prevent the clot from getting larger.
• To stop the clot from traveling to your lungs.
• To lower the chance of another blood clot forming.

Treatment may include:

• Blood thinners (anticoagulant medicines). These medicines lower the ability of the blood to clot. They are a main treatment for DVT. These medicines may be given as a shot, through an I.V. (intravenous) line into a vein, or in pill form. The most common side effect of blood-thinning medicine is bleeding.
• Clot busters (fibrinolytics or thrombolytics). These medicines are used to break up clots.
• Inferior vena cava filter. In some cases, a filter is placed in the vena cava. This is the large vein that returns blood from the body to the heart. This filter prevents clots from reaching the heart and lungs.

The possible complications of DVT are:

• Pulmonary embolus. This can cut off blood flow to all or part of the lung. PE may develop quickly. It's a medical emergency and may cause death.
• Chronic venous insufficiency. This may happen after a blood clot in a leg vein. It means that a vein no longer works well. It's a long-term condition where blood pools in the vein instead of flowing back to the heart. Pain and swelling in the leg are common symptoms.
• Post-thrombotic syndrome. This health problem may also happen after a blood clot in a leg vein. It may occur in the weeks or months following a DVT. It's a long-term problem. It causes pain, swelling, and redness. Ulcers and sores can also develop. All these symptoms may make it hard to walk and take part in daily activities.

You can help prevent DVT with these steps:

• Take blood thinners, if your doctor has prescribed them for you.
• Wiggle your toes and move your ankles if you sit or lie down for long periods of time.
• Walk. Get up and move as soon as possible after surgery or illness.
• Wear elastic or compression stockings, if your doctor has prescribed them.

If you are in the hospital, your risk for blood clots increases. Your doctor may prescribe the use of a sequential compression device or intermittent pneumatic compression. Special sleeves go around both legs. They are attached to a device that applies gentle pressure to the legs. Remove the sleeves so that you don't trip or fall when you are walking, such as when you use the bathroom or shower. Ask for help if you can't remove and replace the sleeves.

When you travel and must sit for long periods of time, you can lower your risk of a blood clot by:

• Walking up and down the aisles (if traveling by plane or bus).
• Stopping about every hour and walking a little (if traveling by car).
• Moving your legs, ankles, and toes while sitting.
• Wearing loose clothing.
• Limiting the amount of alcohol you drink.
• Drinking a lot of water.
• Talking with your doctor about a program of regular exercise.
• Staying at a healthy weight.
• Quitting smoking, if you smoke.

If you have symptoms that may indicate a blood clot in the lungs, call 911 or get emergency help. Symptoms of a blood clot in the lungs include:

• Chest pain.
• Trouble breathing.
• Coughing (may cough up blood).
• A fast heartbeat.
• Sweating.
• Fainting.

If you are taking blood thinners, report bruising or bleeding to your healthcare provider right away or get medical care right away. Symptoms may include:

• Blood in the urine.
• Bleeding with bowel movements.
• A bloody nose.
• Bleeding gums.
• A cut that won't stop bleeding.
• Vaginal bleeding.

• DVT is a blood clot or thrombus in a deep vein. These blood clots are most common in the leg. But they can develop in other parts of the body.
• When blood moves too slowly, it can pool in the veins. This makes a clot more likely to form.
• Some risk factors for DVT are being overweight, being older than age 60, and spending a long period of time not moving, such as while staying in a hospital.
• The symptoms of DVT are pain, swelling, and redness in the leg, arm, or other area.
• Treatment may include medicines, such as blood thinners and clot busters.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions.