Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)

DEEP VEIN THROMBOSIS OVERVIEW — Venous thrombosis is a condition in which a blood clot (thrombus) forms in a vein. This clot can limit blood flow through the vein, causing swelling and pain. Most commonly, venous thrombosis occurs in the "deep veins" in the legs, thighs, or pelvis (figure 1). This is called a deep vein thrombosis, or DVT.

DVT in the leg is the most common type of venous thrombosis. However, a clot can form anywhere in the venous system. If a part or all of the blood clot in the vein breaks off from the site where it is formed, it can travel through the venous system; this is called an embolus. If the embolus lodges in the lung, it is called a pulmonary embolus (PE), a serious condition that leads to over 50,000 deaths a year in the United States. In most cases, PE is caused when part of a DVT breaks off and lodges in the lung. The term "venous thromboembolism" describes both DVT and PE.

This topic review discusses the risk factors, signs and symptoms, diagnostic process, and treatment of a DVT. The diagnosis and treatment of PEs are discussed separately. (See "Patient education: Pulmonary embolism (Beyond the Basics)".)

DEEP VEIN THROMBOSIS RISK FACTORS — There are several factors that can increase your risk of developing a DVT.

If a person is found to have a DVT and there is no known medical condition or recent surgery, leg injury, or immobility that could have caused the DVT, it is possible that an inherited condition is the cause. This is especially true in people with a family member who has also experienced a DVT or pulmonary embolus (PE). In these cases, testing for an inherited thrombophilia (a genetic problem that causes the blood to form abnormal clots more easily than normal) may be recommended. However, finding an inherited thrombophilia often does not change the way that doctors treat the DVT and may not increase the chance of having another blood clot in the future (see 'Finding the cause of a blood clot' below). Therefore, it is not always necessary or helpful to test for an inherited thrombophilia.

Medical conditions or medications — Some medical conditions and medications increase your risk of developing a blood clot:

●Cancer.

●Immobilization (eg, due to hospitalization, recovery from injury, bedrest, or paralysis).

●Previous DVT or PE.

●Older age, especially being older than 65 years.

●Obesity.

●Pregnancy.

●Certain medications (eg, birth control pills, hormone replacement therapy, tamoxifen, thalidomide, erythropoietin, cancer chemotherapy medications). The risk of a blood clot is further increased in people who use one of these medications and also have other risk factors.

●Smoking.

●Heart failure.

●Coronavirus disease 2019 (COVID-19) infection (associated with hospitalization).

●Kidney problems, such as nephrotic syndrome. (See "Patient education: The nephrotic syndrome (Beyond the Basics)".)

Cancer — People with cancer, especially if they are receiving treatment (eg, with chemotherapy or radiation therapy), are at particularly increased risk for developing DVT or PE.

Surgery and related conditions — Surgical procedures, especially those involving the hip, pelvis, or knee, increase a person's risk of developing a blood clot. During the recovery period, prolonged inactivity can also increase the risk of developing a blood clot. Measures to help reduce the risk of blood clots are discussed below. (See 'Deep vein thrombosis prevention' below.)

Inherited thrombophilia — Inherited thrombophilia refers to a genetic problem that causes the blood to form abnormal clots more easily than normal. Various factors in the blood clotting process may be involved, depending on the type of genetic problem present.

People diagnosed with a venous thromboembolism are occasionally found to have an inherited thrombophilia. Examples of inherited thrombophilia include factor V Leiden, the prothrombin gene mutation, and deficiencies of naturally occurring blood thinning factors (antithrombin, protein C, and protein S).

Acquired thrombophilia — Some types of thrombophilia are not inherited but can still increase a person's risk of developing a blood clot. Examples include:

●Certain disorders of the blood, such as polycythemia vera or essential thrombocytosis

●Antiphospholipid antibodies (antibodies in the blood that can affect the clotting process) (see "Patient education: Antiphospholipid syndrome (Beyond the Basics)")

●Having an increased level of one or more factors involved in blood clotting

DEEP VEIN THROMBOSIS SYMPTOMS — The signs and symptoms of DVT are nonspecific, may be caused by the clot itself, or may be related to another condition. Imaging studies may be needed to differentiate if a clot is present or if the signs and symptoms are due to another condition.

Deep vein thrombosis — Classic symptoms of DVT include swelling, pain, warmth and tenderness to touch, and redness in the involved leg.

Superficial phlebitis — Superficial phlebitis (SP) causes pain, tenderness, firmness, and/or redness in a vein due to inflammation, infection, and/or a blood clot (thrombus). It is most commonly seen in the inner part of the lower legs. SP differs from a DVT because the veins that are affected are near the surface of the skin. The clots cannot break off to go the lungs to cause a pulmonary embolus. However, if the involved veins are very large and close to the deeper veins, SP can turn into a DVT.

DEEP VEIN THROMBOSIS DIAGNOSIS — If your history, symptoms, and physical examination suggest a DVT, you will need tests to confirm the diagnosis. Tests may include a blood test called D-dimer and compression ultrasonography of the leg veins and/or other imaging tests.

If a person with a DVT also has signs or symptoms of a pulmonary embolus (PE), additional testing may be needed. (See "Patient education: Pulmonary embolism (Beyond the Basics)".)

Diagnostic tests

D-dimer — D-dimer is a substance in the blood that is often increased in people with DVT or PE, as well as other conditions associated with infection or inflammation. D-dimer testing is sometimes useful for patients with a suspected DVT or PE. If the D-dimer test is negative and you have a low risk of DVT or PE based on your history and physical examination, DVT or PE are unlikely and further diagnostic testing may not be needed.

Compression ultrasonography — Compression ultrasonography uses sound waves to generate pictures of the structures inside the leg. For this type of examination, you lie on your back and then stomach as an ultrasound wand is applied to the leg. In most circumstances, compression ultrasonography is the test of choice for patients with suspected DVT.

Other imaging tests — Although no longer used widely for diagnosis, in some cases (eg, if it is not possible to perform ultrasonography for some reason) another imaging test may done. These include magnetic resonance imaging (MRI; which uses a strong magnet to produce detailed pictures of the inside of the body) and computed tomography (CT) scan.

Finding the cause of a blood clot — After confirming that DVT or PE is present, the health care provider will want to know what caused it. In many cases, there are obvious risk factors such as recent surgery or immobility. In other cases, the clinician may test for the presence of a thrombophilia or for another medical condition associated with an increased risk for venous thrombosis (such as cancer). (See 'Inherited thrombophilia' above and 'Deep vein thrombosis risk factors' above.)

People with some acquired or inherited abnormalities may require additional treatment or prevention measures to reduce the risk of another thrombosis. Screening family members for an inherited thrombophilia is controversial. If you have a genetic condition, or are concerned that you might have one, your doctor or a genetic counselor can talk to you about what it means as well as the pros and cons of screening other family members.

DEEP VEIN THROMBOSIS TREATMENT — In treating DVT, the main goal is to prevent the clot from getting bigger and to prevent it from breaking off to cause a pulmonary embolus (PE). Other goals of treatment include preventing the clot from becoming larger, preventing new blood clots from forming, and preventing long-term complications.

The treatment of DVT and PE are similar. In both cases, the primary approach is anticoagulation. Other available treatments, which may be used in specific situations, include thrombolytic therapy or placing a filter in a major blood vessel (the inferior vena cava).

Anticoagulation — Anticoagulants are medications that are commonly called "blood thinners." They do not actually dissolve the clot but rather help to prevent new blood clots from forming. There are several different medications that might be given after a DVT diagnosis (referred to as "initial anticoagulation"), including:

●Direct oral anticoagulants (DOACs) – These are available in pill form; those available, depending on the country, for initial anticoagulation are apixaban (eg, brand name: Eliquis), dabigatran (eg, brand name: Pradaxa), edoxaban (eg, brand name: Savaysa), or rivaroxaban (eg, brand name: Xarelto).

●Low-molecular-weight (LMW) heparin, which is given as an injection under the skin – Options include dalteparin (brand name: Fragmin), enoxaparin (brand name: Lovenox), and tinzaparin (brand name: Innohep).

●Fondaparinux (brand name: Arixtra), also given by injection.

●Unfractionated heparin, which is given into a vein (intravenously) or as an injection under the skin – This may be the preferred choice in certain circumstances, such as if a person requires dialysis for kidney failure.

Initial anticoagulation usually consists of 5 to 10 days of treatment with LMW heparin, unfractionated heparin, or fondaparinux. After that, long-term anticoagulation is continued for 3 to 12 months (see 'Duration of treatment' below). DOACs are also an option for long-term anticoagulation. An advantage of initiating treatment with a DOAC is that some DOACs (apixaban, rivaroxaban) can be started right after a clot is diagnosed without the need for an initial 5 to 10 days of an injectable blood thinner (eg, LMW heparin). In some situations, another oral medication called warfarin (sample brand name: Coumadin) can be given instead of a DOAC. If you take warfarin, you need to get regular blood tests to monitor the blood thinning effect of warfarin to ensure that you are taking the right dose; this is not needed for patients on DOACs (see "Patient education: Warfarin (Beyond the Basics)"). Less commonly, injections (once or twice a day) of LMW heparin or fondaparinux are used for the entire treatment period. In rare circumstances, unfractionated heparin as an injection can also be given.

The choice of anticoagulant depends upon multiple factors, including your preference, your doctor's recommendation based on your situation and medical history, and cost considerations.

Duration of treatment — Anticoagulation is recommended for a minimum of three months in a patient with DVT.

●If you had a reversible risk factor contributing to your DVT, such as trauma, surgery, or being confined to bed for a prolonged period, you will likely be treated with anticoagulation for only three months or until the risk factor has resolved.

●Expert groups suggest that people who develop a DVT but do not have a known risk factor may need treatment with an anticoagulant for an indefinite period of time. However, if this is your situation, you should discuss the pros and cons with your doctor after three months of treatment. If the decision is made to continue anticoagulation, your doctor will continue to reassess on a regular basis. Some people prefer to continue the anticoagulant, which may carry an increased risk of bleeding, while others prefer to stop the anticoagulant at some point, which may carry an increased risk for repeat thrombosis.

●Most experts recommend continuing anticoagulation indefinitely for people with two or more episodes of venous thrombosis or if a risk factor for clotting persists (eg, antiphospholipid syndrome, cancer).

Walking during deep vein thrombosis treatment — Once an anticoagulant has been started and symptoms (such as pain and swelling) are under control, you are strongly encouraged to get up and walk around periodically. Studies show that there is no increased risk of complications (eg, pulmonary embolus) in people who get up and walk, and walking may in fact help you feel better faster.

Thrombolytic therapy — In some severe life-threatening cases, a health care provider will recommend an intravenous medicine to dissolve blood clots (ie, a "clot-busting" medication). This is called thrombolytic therapy. This therapy is reserved for people who have serious complications related to DVT or PE and who have a low risk of serious bleeding as a side effect of the therapy. The response to thrombolytic therapy is best when there is a short time between the diagnosis of DVT/PE and the start of thrombolytic therapy.

Inferior vena cava filter — An inferior vena cava (IVC) filter is a device that blocks the circulation of clots in the bloodstream, especially the movement of a clot from the legs to the lungs. It is placed in the IVC (the large vein leading from the lower body to the heart). The IVC filter typically is inserted through a small incision in a leg vein with the use of a local anesthetic. An IVC filter may be recommended in people with venous thromboembolism who cannot use anticoagulants because of a very high bleeding risk. However, in the long term, IVC filters can actually increase the risk of developing blood clots.

DEEP VEIN THROMBOSIS PREVENTION

People with cancer — In selected situations, such as in people undergoing treatment for cancer who are at high risk for DVT (eg, people with stomach or pancreatic cancer who are receiving chemotherapy), anticoagulants may be considered for use to prevent a DVT from occurring.

During hospitalization — Some people who are in the hospital, either for surgery (especially bone or joint surgery and cancer surgery) or because of a serious medical illness, may be given anticoagulants to decrease the risk of blood clots. Anticoagulants may also be given to women at high risk for venous thrombosis during and after pregnancy. (See 'Deep vein thrombosis risk factors' above.)

In people who are hospitalized and have a moderate to low risk of blood clots, other preventive measures may be used. For example, some people are fitted with inflatable compression devices after surgery. These devices are worn around the legs during and immediately after surgery and periodically fill with air. These devices apply gentle pressure to improve circulation and help prevent clots. Compression stockings may also be recommended.

In all cases, walking as soon as possible after surgery can decrease the risk of a blood clot; it can also decrease the risk of chronic swelling in the legs from your DVT (also known as "post-thrombotic syndrome").

Extended travel — Prolonged travel (eg, taking an airplane flight or car ride that lasts more than five hours) appears to increase the risk of developing blood clots, although the risk is very small. There are a few tips that may be of benefit during extended travel (table 1).

SPECIAL PRECAUTIONS FOR PEOPLE WITH DEEP VEIN THROMBOSIS

Risk of developing another clot — People being treated for venous thrombosis are at an increased risk for developing another blood clot, although this risk is significantly lower when an anticoagulant is used. Therefore, taking your blood thinners exactly as directed is important to reduce the risk of a recurrent blood clot. Watch for new leg pain, swelling, and/or redness; if any of these symptoms occur, call your doctor or seek medical attention as soon as possible.

Other symptoms may indicate that a clot in the leg has broken off and traveled to the lung, causing a pulmonary embolus (PE). These may include:

●New chest pain with difficulty breathing

●A rapid heart rate and/or a feeling of lightheadedness or dizziness

A PE can be life-threatening and requires immediate attention. If you have the above symptoms, call for help right away. (In the United States and Canada, call 9-1-1 for an ambulance.)

Bleeding risk — Anticoagulants should be taken exactly as directed to minimize the risk of serious bleeding. If you forget or miss a dose, call your health care provider or clinic for advice. Do not try to take an extra dose or change the dose yourself unless your doctor specifically tells you to. If you get a refill of your medication and the pills or tablets look different from the last bottle, let your doctor or pharmacist know right away. If you take warfarin, there are other things you need to be aware of as well; these are discussed in detail in a separate topic review. (See "Patient education: Warfarin (Beyond the Basics)".)

You are more likely to bleed while taking anticoagulants. Bleeding may develop in many areas, such as bleeding from the nose or gums, excessive menstrual bleeding, bleeding in the urine or feces, bleeding or excessive bruising in the skin, or vomiting material that is bright red or looks like coffee grounds. In some cases, if there is internal bleeding, you may not notice right away. Bleeding inside the body can cause you to feel faint or have pain in the back or abdomen. Call your health care provider right away if you have these symptoms. It's also important to call immediately if you have an injury that could cause internal bleeding, such as a fall, a head injury, or a car accident.

Some simple modifications can reduce your risk of bleeding. For example, you can:

●Use a soft bristle toothbrush.

●Use a humidifier to help reduce nosebleeds (if you live in a cold or dry climate).

●Use caution when handling sharp objects (eg, knives).

●Avoid activities that could result in injury (eg, contact sports).

●Use appropriate safety equipment (eg, helmets, padding) during physical activity.

●Avoid aspirin or other nonsteroidal antiinflammatory agents (NSAIDS; eg, ibuprofen [sample brand names: Advil, Motrin] and naproxen [sample brand name: Aleve]) unless your health care provider tells you to take them. Other nonprescription pain medications, such as acetaminophen (sample brand name: Tylenol), may be safe alternatives.

Wear an alert tag — While you are taking anticoagulants, wear a medical bracelet, necklace, or similar alert tag that includes the name of your anticoagulant at all times. If you end up needing treatment and are unable to explain your condition, the tag will alert responders that you are on an anticoagulant and at risk of excessive bleeding. Many anticoagulants have good antidotes or reversal agents available, so it is important for responders to know the name of the anticoagulant you are taking.

The alert tag should list your medical conditions as well as the name and phone number of an emergency contact. Some alert tags provide a toll-free number that emergency medical workers can call to find out your medical history, list of medications, family emergency contact numbers, and health care provider names and numbers.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (http://www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Varicose veins and other vein disease in the legs (The Basics)
Patient education: Deep vein thrombosis (blood clot in the leg) (The Basics)
Patient education: Staying healthy when you travel (The Basics)
Patient education: Swelling (The Basics)
Patient education: Deciding to have a hip replacement (The Basics)
Patient education: Deciding to have a knee replacement (The Basics)
Patient education: Pulmonary embolism (blood clot in the lung) (The Basics)
Patient education: Choosing an oral medicine for blood clots (The Basics)
Patient education: Taking oral medicines for blood clots (The Basics)
Patient education: Duplex ultrasound (The Basics)
Patient education: Factor V Leiden (The Basics)
Patient education: Patent foramen ovale (The Basics)
Patient education: Superficial vein phlebitis and thrombosis (The Basics)
Patient education: Vein ablation (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Pulmonary embolism (Beyond the Basics)
Patient education: The nephrotic syndrome (Beyond the Basics)
Patient education: Antiphospholipid syndrome (Beyond the Basics)
Patient education: Warfarin (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Use of anticoagulants during pregnancy and postpartum
Deep vein thrombosis in pregnancy: Epidemiology, pathogenesis, and diagnosis
Venous thromboembolism in pregnancy: Prevention
Venous thromboembolism in pregnancy and postpartum: Treatment
Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity
Cerebral venous thrombosis: Etiology, clinical features, and diagnosis
Evaluating adult patients with established venous thromboembolism for acquired and inherited risk factors
Approach to thrombolytic (fibrinolytic) therapy in acute pulmonary embolism: Patient selection and administration
Risk and prevention of venous thromboembolism in adults with cancer
Placement of vena cava filters and their complications
Prevention of venous thromboembolism in adults undergoing hip fracture repair or hip or knee replacement
Perioperative management of patients receiving anticoagulants
Overview of the causes of venous thrombosis
Prevention of venous thromboembolic disease in acutely ill hospitalized medical adults
Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients
Heparin and LMW heparin: Dosing and adverse effects
Warfarin and other VKAs: Dosing and adverse effects
Overview of the treatment of proximal and distal lower extremity deep vein thrombosis (DVT)
Antithrombin deficiency
Protein S deficiency
Protein C deficiency
Factor V Leiden and activated protein C resistance
Prothrombin G20210A

The following organizations also provide reliable health information.

●Anticoagulation Forum (www.acforum.org)

●Thrombosis Canada (www.thrombosiscanada.ca)

●National Blood Clot Alliance (www.stoptheclot.org/)