Deep Vein Thrombosis (DVT)

DVT (Blood Clot in the Leg, Deep Vein Thrombosis) Definition and Facts

Illustration of a blood clot forming in a blood vessel.
Blood clots often require medical treatment.

  • The definition of deep venous thrombosis (DVT) is a condition in which a blood clot is embedded in one of the major deep veins of the lower legs, thighs, pelvis, or arm. A clot blocks blood circulation through these veins, which carry blood from the lower body back to the heart. The blockage can cause acute pain, swelling, or warmth in the affected leg.
  • Blood clots in the veins can cause inflammation (irritation) called thrombophlebitis.
  • Severe complications of deep vein thrombosis occur when a clot breaks loose (or embolizes) and travels through the bloodstream, causing blockage of blood vessels (pulmonary arteries) in the lung. Called pulmonary embolism (PE), this can lead to severe difficulty in breathing and even death, depending on the degree of blockage.
  • The U.S. Centers for Disease Control and Prevention (CDC) estimates as many as 900,000 people could be affected by DVT/PE each year in the United States, and 60,000 to 100,000 Americans die of DVT/PE (also called venous thromboembolism).
  • Symptoms and signs of DVT occur in the leg with the blood clot, and include:
    • Swelling
    • Pain
    • Redness
    • Warmth to the touch
    • Worsening leg pain when bending the foot
    • Leg cramps (especially at night and/or in the calf)
    • Discoloration of skin
  • Causes of deep vein thrombosis include damage to the inside of a blood vessel due to trauma or other conditions, changes in normal blood flow, or a rare state in which the blood is more likely than usual to clot (hypercoagulability).
  • Risk factors for DVT/PE include:
    • Prolonged sitting or immobility
    • Recent surgery
    • Recent trauma to the lower body
    • Obesity
    • Heart attack or heart failure
    • Pregnancy or recent childbirth
    • High altitudes
    • Estrogen therapy or birth control pills
    • Cancer
    • Rare genetic conditions that affect blood clotting factors
    • Certain heart or respiratory conditions
    • Advanced age
    • Medical conditions that affect the veins
  • Doctors diagnose the condition using imaging tests such as Doppler ultrasound, venography, impedance plethysmography, and CT scan.
  • Treatment of DVT in the leg is individualized for each patient. Usually, anticoagulation or blood-thinning medication is prescribed to prevent further clot formation and to minimize the risk that part of the blood clot will break off and travel to the lung and cause pulmonary embolism. New guidelines for various treatments were made by the ACCP (American College of Physicians) in 2016.
  • In rare cases, large deep venous thrombosis of the leg is treated with surgery in patients who cannot take blood thinners.
  • Prevention and prophylaxis of DVT involves managing risk factors.
    • Lose weight if overweight or obese
    • Avoid periods of prolonged immobility.
    • Keep the legs elevated while sitting down or in bed.
    • Avoid high-dose estrogen pills.
    • After surgery, get out of bed several times a day during the recovery period, use compression devices on the legs or elastic compression socks/stockings.
    • Take heparin or warfarin (Coumadin, Jantoven) if prescribed to prevent clot formation.

What Are the Warning Signs and Symptoms of a DVT?

DVT (Blood Clot in the Leg)
Symptoms of DVT (blood clot in the leg) include swelling, pain, redness, warmth to the touch, leg cramps, or bluish/whitish discoloration of the skin.

Signs and symptoms of a blood clot in the leg or deep vein thrombosis occur in the affected leg when a clot obstructs blood flow and causes inflammation. Signs and symptoms of DVT may include:

  1. Swelling
  2. Gradual onset of pain
  3. Redness
  4. Warmth to the touch
  5. Worsening leg pain when bending the foot
  6. Leg cramps, especially at night, and often starting in the calf
  7. Bluish or whitish discoloration of skin

Some people with deep vein thrombosis do not experience any symptoms.

What Causes DVTs?

Causes of DVT
The three factors that may lead to blood clots are damage to the inside of a blood vessel, blockage of blood flow, and hypercoagulability (rare state).

Three factors may lead to the formation of a clot inside a blood vessel:

  1. Damage to the inside of a blood vessel due to trauma or other conditions
  2. Changes in normal blood flow, including unusual turbulence, or partial or complete blockage of blood flow
  3. Hypercoagulability, a rare state in which the blood is more likely than usual to clot

Any event or condition that can lead to blood vessel damage, hypercoagulability, or change in blood flow can potentially cause deep vein thrombosis. The more common risk factors are:

  • Prolonged sitting, such as during a long plane flight or car ride
  • Prolonged bed rest or immobility, such as after injury or during illness (for example stroke)
  • Recent surgery, particularly orthopedic (especially hip, leg, or , knee such as knee or hip replacement), gynecologic, heart, or abdominal surgery
  • Recent trauma to the lower body, such as fractures of the bones of the hip, thigh, or lower leg
  • Obesity
  • Heart attack or heart failure
  • Pregnancy or recent childbirth
  • Being at very high altitude, greater than 14,000 feet
  • Use of estrogen therapy or birth control pills
  • Cancer
  • Rare inherited genetic conditions that lead to changes in certain blood clotting factors
  • Certain heart or respiratory conditions
  • Advanced age
  • Medical conditions that affect the veins such as vasculitis (inflammation of the vein walls), varicose veins
  • Superficial venous thrombosis (SVT) occurs when a blood clot forms in a superficial vein near the surface of the body. While not the same as DVT (which occurs in deep veins) it can be a risk factor for DVT/PE
  • Disseminated intravascular coagulation (DIC), a medical condition in which blood clotting occurs inappropriately, usually is caused by overwhelming infection or organ failure

If an individual has one deep vein thrombosis, they are 33% more likely to develop a second deep vein thrombosis within 10 years.

When Is a DVT a Medical Emergency?

Call the doctor immediately if a blood clot is suspected.

  • Although a deep vein thrombosis may resolve on its own, the life-threatening consequences of a clot reaching the lung, called pulmonary embolism, are severe enough to warrant seeking medical attention immediately.
  • The doctor may tell the patient to go immediately to a hospital emergency department.

If a person has leg pain or swelling with any risk factors, go to a hospital emergency department immediately.

Call 9-1-1 if you or someone you know with a current deep vein thrombosis, previous deep vein thrombosis, or other DVT/PE risk factor begins having chest pain, shortness of breath, difficulty breathing, fainting, or any other concerning symptom.

Which Types of Doctors Treat DVTs?

The initial diagnosis of DVT is usually made by the general practitioner, internist, family practitioner, or an emergency medicine specialist.

Depending on the severity of the DVT/PE, or the need for intervascular or surgical intervention, one may be referred to a vascular surgeon or an interventional radiologist. Other specialists involved in the care may involve a pulmonologist (a physician who specializes in the lungs), or a hematologist (specialist in blood disorders).

What Tests Diagnose DVTs?

Upon hearing the patient's symptoms, the doctor may suspect the patient has a deep vein thrombosis, especially if any risk factors are present.

No accurate blood test is available to diagnose deep vein thrombosis. A variety of imaging tests are used to confirm the diagnosis.

  • Doppler ultrasound: Using high-frequency sound waves, this system can visualize the large, proximal veins and detect a clot if one is present. Painless and without complications, this is the most commonly used method to diagnose deep vein thrombosis. However, sometimes the test can miss a clot, especially in the smaller veins.
  • Venography: A liquid dye is injected into the veins for imaging studies. It highlights blockage of blood flow by a clot. This is the most accurate test, but also the most uncomfortable and invasive. It is rarely done today because of the availability of improved ultrasound technology.
  • Impedance plethysmography: Electrodes are used to measure volume changes within veins. Because this test does not detect clots better than ultrasound and is harder to perform, it is rarely used.
  • CT scan: This is a type of X-ray that gives a very detailed look at the leg veins in cross section and can detect clots. It is rarely used for this purpose as it is more difficult to interpret and is time consuming. The CT scan is more useful for identification of blood clots in the lung.

What Is the Treatment for DVTs?

The treatment of blood clots depends upon their location in the body. Most commonly, anticoagulation or blood-thinning medication is prescribed to prevent further clot formation and to minimize the risk that part of the blood clot will break off and travel to the lung and cause pulmonary embolism, or pulmonary embolism. Treatment of deep venous thrombosis in the leg is often individualized for each patient depending upon the clinical situation and other medical conditions that may be present. The following is how various drugs and therapies have been used. New guidelines have been written in 2016 to help optimize treatments in patients with or without cancer, lower extremity DVT and pulmonary embolism, and for other individual patient circumstances.

Treatment of deep venous thrombosis in the leg is often individualized for each patient depending upon the clinical situation and other medical conditions that may be present.

Anticoagulation is usual the treatment of choice and is a two stage process. Low molecular weight heparin (enoxaparin [Lovenox], dalteparin [Fragmin]) injections are started to begin immediate blood thinning. At the same time, warfarin (Coumadin, Jantoven) is prescribed (an oral anticoagulation medication that takes a few days to become effective and adequately anticoagulate the blood). Blood tests (prothrombin time or international normalized ratio [INR]) are used to measure the effectiveness of the warfarin therapy. When the INR reaches the appropriate level, the heparin injections are discontinued.

Rivaroxaban (Xarelto) is a medication called a selective Factor Xa inhibitor that is an oral tablet indicated for the treatment of DVT. It may be used as a treatment and a preventative prophylaxis for blood clots instead of warfarin.

Apixaban (Eliquis) and dabigatran (Pradaxa) also are drugs used to prevent blood clots and treat acute DVT.

If possible, the treatment of uncomplicated deep venous thrombosis in an individual is accomplished as an outpatient. Education is provided to the patient and family to teach them how to administer the injection, and the patient is instructed to return to their family physician or the hospital for appropriate monitoring (blood tests). Some patients will need to be admitted to the hospital if they have significant underlying medical illnesses, are pregnant, or are unable to administer the heparin injections.

The duration of anticoagulation therapy depends upon the circumstances that led to the development of the blood clot. If there were temporary risk factors, for example a long trip or recent immobility because of injury or illness, treatment may last 3 to 6 months. However, if the cause is unknown or if there is the risk for recurrent clot formation, medication may be required for more than 12 months.

Not all DVTs require anticoagulation. Because small clots located in veins below the knee have a low risk of embolizing to the lung, it can be possible to observe the patient without giving medications. Using serial ultrasound tests of the veins, the clot can be monitored to see whether it is extending and growing or whether it is stable and needs no further treatment.

Blood clots located in the femoral vein near the groin that extend into the iliac vein in the abdomen may require more aggressive treatment with thrombolytic (thrombo=clot + lysis=breakdown) therapy. Clot-busting drugs (alteplase [Activase], streptokinase [Streptase]) may be injected directly into the clot itself. This usually requires a specialist (a vascular surgeon or an interventional radiologist) who can use fluoroscopy or real time X-rays to position a catheter or tube into the affected vein where the clot resides and drip the medication in over a period of time to dissolve the clot and prevent it from traveling to the lung.

Similar situations can exist in the arm. DVTs above the elbow are usually treated with blood-thinner medications as described above, while clots in the subclavian vein, located just below the collarbone, may be considered for thrombolytic therapy.

Because of underlying medical conditions, some people may not be able to take anticoagulation medications and may require an alternative treatment instead of medication. Those who have gastrointestinal bleeding (bleeding from the stomach or bowel), intracranial bleeding (bleeding inside the brain or surrounding tissues), or who have had recent major trauma potentially could bleed to death if anticoagulation medications are prescribed. The alternative for leg DVT treatment in these situations may be an inferior vena cava filter. The vena cava is the large vein that collects blood from the lower body just before it enters the heart. A filter can be placed into the vena cava to trap any clots that might break off and prevent them from traveling to the heart and then to the lungs.

Compression stockings or socks are useful in preventing a complication of a leg blood clot called post-thrombotic syndrome or postphlebitis syndrome, in which the affected leg swells and becomes chronically painful. These stockings may be purchased over-the-counter or can be custom fitted. It is recommended they be worn for at least a year after the diagnosis of deep venous thrombosis.

What Medications Treat DVTs?

Warfarin (Coumadin) is an oral medication taken to thin or anticoagulate the blood. It may take a few days for its action to take effect. The dose needs to be individualized for each person, and blood clotting must be monitored routinely since changes in diet, activity, and the administration of other medications may affect the levels of warfarin. Blood tests (usually international normalized ratio [INR]) are done routinely to monitor the blood-thinning effects and help the health care professional select the appropriate warfarin dose. Ideally, the INR should be kept in a range between 2.0 and 3.0. Blood tests are done weekly until the INR stabilizes and then are done every 2 weeks to every month.

Enoxaparin (Lovenox) is a low molecular weight heparin injected beneath the skin to thin the blood. The dose is usually 1 milligram per kilogram of weight injected twice daily or 1.5 milligrams per kilogram injected once daily. Enoxaparin usually is considered a temporary medication to be used to thin the blood while warfarin begins to take effect; however, it may be used over the long term in some patients with cancer. Fondaparinux (Arixtra) is another injectable chemically related to low molecular weight heparin, used for DVT prevention and treatment.

If a woman develops a DVT/PE while pregnant it is usually treated with heparin only, because warfarin is dangerous to administer during pregnancy.

Rivaroxaban (Xarelto) is a newer medication, which belongs to the selective Factor Xa inhibitor class of drugs, is an oral tablet for the treatment of DVT. It may be used as a treatment and a preventive therapy for blood clots.

Apixaban (Eliquis), dabigatran (Pradaxa), and Edoxaban (Savaysa, Lixiana) are also used to prevent blood clots and treat acute DVT.

When Is Surgery Necessary for a DVT?

Surgery is a rare option in treating large deep venous thrombosis of the leg in patients who cannot take blood thinners or who have developed recurrent blood clots while on anticoagulant medications. The surgery is usually accompanied by placing an IVC (inferior vena cava) filter to prevent future clots from embolizing to the lung.

Phlegmasia cerulea dolens describes a situation in which a blood clot forms in the iliac vein of the pelvis and the femoral vein of the leg, obstructing almost all blood return and compromising blood supply to the leg. In this case surgery may be considered to remove the clot, but the patient will also require anticoagulant medications.

Do I Need to Follow-up with My Doctor After DVT Treatment?

A person who has had a deep vein thrombosis may be asked to return for follow-up. Doppler ultrasounds or other imaging studies may be performed if the leg swelling persists or if the symptoms recur. During anticoagulant treatment, it is often advised to take the following measures:

  • Take the prescribed amount of medication as directed by a physician. Do not miss or add doses.
  • Follow the doctor's instructions closely about when to get lab tests for blood coagulation.
  • Ask the doctor before starting or stopping any medication or supplement, including over-the-counter (OTC) medications. Many medicines and supplements increase or otherwise interfere with the effect of anticoagulants.
  • Ask what foods should be avoided, because some foods may change the effectiveness of blood-thinning drugs.
  • Wearing a MedicAlert bracelet with information about any anticoagulants one is taking is advised.
  • People on anticoagulant therapy should inform any other medical professionals including dentists or podiatrists before undergoing any procedure.

What Is the Risk of Having Another DVT?

Most DVTs resolve on their own. If a pulmonary embolism (PE) occurs, the prognosis can be more severe.

  • About 25% of people who have a PE will die suddenly, and that will be the only symptom.
  • About 23% of people with PE will die within 3 months of diagnosis, just over 30% will die after 6 months, and there is a 37% mortality (death) rate at 1 year after being diagnosed.

If an individual has had one deep vein thrombosis, they are more likely than the average person to have another deep vein thrombosis.

  • The CDC estimates 33% of people with DVT/PE will have a recurrence within 10 years.
  • Recurrence of DVT is more common in patients with risk factors such as cancer or inherited blood-clotting problems. Recurrence is less common in patients who have short-term risk factors, such as surgery or temporary inactivity.
  • Closely follow the prevention instructions from the doctor.
  • Anticoagulant therapy lowers the death rate from pulmonary embolism significantly.

How Can a DVT Be Prevented?

The key to prevention of DVT is to reverse any risk factors, for example:

  • Lose weight if overweight or obese.
  • Avoid periods of prolonged immobility. Get up and move around every 15 to 30 minutes during long plane flights. Do simple stretching exercises while seated. Make frequent stops and get out of the car when driving long distances.
  • Keep the legs elevated while sitting down or in bed.
  • Avoid high-dose estrogen pills, unless they are deemed necessary by the doctor.

In the case of recent surgery, preventive treatment may be prescribed to avoid formation of a clot.

  • The patient may be instructed to get out of bed several times a day during the recovery period.
  • Sequential compression devices (SCDs) may be placed on the legs. Their squeezing action has been shown to reduce the probability of clot formation. The patient may also be given elastic compression socks or stockings to wear.
  • Low-molecular-weight heparin or low-dose warfarin may be prescribed to prevent clot formation.

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DVT picture

What Are the Symptoms and Signs of a Pulmonary Embolism (Blood Clot in the Lung)?

Warning signs and symptoms of a blood clot in the lung or pulmonary embolism include:

  1. A very sharp stabbing pain in the chest
  2. Shortness of breath.
  3. Cough.
  4. Sweating.
  5. Passing out.

A blood clot in the lung is a medical emergency and needs to be treated right away.

LiP, GYH MD. Approach to the diagnosis and therapy of lower extremity deep vein thrombosis. UpToDate. Updated: Sep 29, 2019.

Centers for Disease Control and Prevention. Venous Thromboembolism. (Blood Clots).

FDA Prescribing Information. SAVAYSA™ (edoxaban).

FDA Prescribing Information. ARIXTRA® (fondaparinux sodium) infection.

Dentali, F., et al. "Pulmonary embolism severity index accurately predicts long-term mortality rate in patients hospitalized for acute pulmonary embolism." Journal of Thrombosis and Haemostasis . 11.12 (2013): 2103-2120.

Litzendorf, M. E. and B Satiani. "Superficial venous thrombosis: disease progression and evolving treatment approaches." Vascular Health and Risk Management. 7 (2011): 569-575.

Lucena, J., et al. "Pulmonary embolism and sudden-unexpected death: prospective study on 2477 forensic autopsies performed at the Institute of Legal Medicine in Seville." Journal of Forensic and Legal Medicine. 16.4 (2009): 196-201.

MedlinePlus. Deep Vein Thrombosis. Thompson, B.T., MD. "Overview of acute pulmonary embolism in adults." Updated: Aug 08, 2016.