deep vein thrombosis

deep vein thrombosis

Credit and © Society of Interventional Radiology.

Deep vein thrombosis 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 the bloodstream, it can lodge in one of the lungs. This is called pulmonary embolism, 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. Blood clots in superficial veins are not dangerous because they can't travel to the lungs.


Who is at risk for deep vein thrombosis?

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

    The risk for deep vein clots increases if a person who has 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 symptoms of deep vein thrombosis or pulmonary embolism appear. 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.

    Pulmonary embolism

    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 taking a deep breath
  • Shortness of breath


    A doctor will obtain a medical history and carry out an examination in order to determine if a person has 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 the 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 the doctor can see the blood flow in the leg. See ultrasound.

  • 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, called a contrast medium, 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 can't 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 a vein and moving to the lungs
  • Reduce the chance of having another blood clot


    Several types of medicine may be used to treat and/or prevent deep vein thrombosis:


  • Anticoagulants decrease the 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).

    A doctor may treat a patient with both heparin and warfarin (Coumadin) 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 can't take warfarin and are treated with heparin only.

    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 the blood clot occurred after a short-term risk (for example, surgery), the treatment may be shorter.
          - In patients who have had clots before, a longer treatment will be needed.
          - In patients who have certain other illnesses, such as cancer, they may need to take anticoagulants for as long as the illness is present.

    The most common side effect of anticoagulants is bleeding. A doctor should be informed right away by patients who 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 can't take heparin.

    Other treatments

    Vena cava filters are used when a patient can't take medicines to thin the blood, or when they 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 doesn't prevent new clots from developing. Graduated dvt 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.

    Treatment tips

    Much of the treatment for deep vein thrombosis takes place at home. It is important to:


  • Take medicines correctly.
  • Have blood tests done as directed by a doctor.
  • Avoid activities that may cause serious injury or bleeding.
  • Talk to a doctor before taking anticoagulants with any other medicines, especially over-the-counter medicines, at the same time. Over-the-counter aspirin, for example, can thin the blood. Taking two medicines that thin your blood (even if one is over-the-counter) may increase the risk for excessive bleeding.
  • Ask a doctor about dietary factors. Foods that contain vitamin K can change how well warfarin works. Vitamin K is found in green leafy vegetables and some oils, such as canola and soybean oil. It is best to eat a well-balanced, healthy diet that doesn't vary greatly.
  • Discuss with a doctor what amount of alcohol is safe to drink if also taking medicine.


    Preventing deep vein thrombosis depends on whether a person has had a clot before and on risk factors for developing a clot.


    If a deep vein clot has developed before, future clots may be prevented by:


  • Taking the medicines prescribed by a doctor to prevent or treat blood clots
  • Following up with a doctor for medicine changes and blood tests

    In the cases where a person has not had a deep vein clot before but has risks factors for developing one, it may be possible to prevent a clot by:


  • Exercising the lower leg muscles, if sitting still for long periods of time.
  • Getting out of bed and moving around as soon as possible after a long period of being bedridden, such as after having surgery or being ill. The sooner a patient moves around, the less chance they have of developing a clot.
  • Taking the medicines prescribed by the doctor to prevent or treat blood clots after some types of surgery.
  • Following up with the doctor.