Deep vein thrombosis occurs when blood clots form, typically, in a deep vein in the leg. Besides leg veins, the condition can affect veins in the pelvis.

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are two parts of the disease known as venous thromboembolism.

DVT is a medical urgency. The Centers for Disease Control and Prevention (CDC) say that 10–30% of people who develop DVT in the leg experience fatal complications within a month of diagnosis.

In this article, we define DVT, explain how to recognize it, and ways to treat it.

a doctor examining a mans calf for symptoms of deep vein thrombosisShare on Pinterest
A person with DVT may experience pain and swelling in the affected limb.

DVT is blood clotting that develops with deep veins, often in the leg or pelvis.

If the thrombus, or clot, breaks off, doctors call this an embolus. Emboli can make their way to the lung, causing a PE.

Clots may also form in the veins of the arm, such as in people with Paget-Schoetter disease.

According to a 2017 review, DVT is the of maternal death in the developed world.

DVT is extremely rare in children. According to a 2016 article, the most recent figures suggest that 0.30 in every 100,000 children under 9 years of age, and 0.64 in every 100,000 children aged between 10 and 19 years develop DVT.

Some people may develop DVT without noticing symptoms. However, if symptoms develop, they may resemble the following:

  • pain in the affected limb that begins in the calf
  • swelling in the affected limb
  • a warm feeling in the swollen, painful region of the leg
  • red or discolored skin

In most people, DVT only develops in one leg. However, on rare occasions, both legs may have DVT.

If a clot dislodges and travels to the lung, the following symptoms may indicate PE:

  • slow breathing or sudden breathlessness
  • chest pain, usually more severe while breathing deeply
  • rapid breaths
  • a faster heart rate

There are two possible complications:

Pulmonary embolism

PE is the most common complication of DVT and can be life threatening. It happens when a piece of a blood clot becomes dislodged and makes its way through the bloodstream into the lungs.

The clot becomes stuck and disrupts the flow of blood in one of the blood vessels in the lung. In mild PE, an individual may not be aware.

A medium sized clot may cause breathing problems and chest pain. In more severe cases, the lung might collapse. PE can lead to heart failure and can be fatal.

Post-thrombotic syndrome

This is more common among people with recurrent DVT. According to a 2016 review, a person with post-thrombotic syndrome might experience the following symptoms, although they vary between individuals:

  • a persistent swelling in the calf
  • a feeling of heaviness in the leg
  • a pulling sensation in the leg
  • an excessively tired leg
  • fluid buildup in the affected leg
  • redness of the skin
  • new varicose veins
  • thickening skin around the area of the DVT
  • leg ulcers for people with severe post-thrombotic syndrome

Some doctors call this condition post-phlebitic syndrome.

An individual may develop DVT when there is no clear cause. However, according to the National Heart, Lung, and Blood Institute (NHLBI), most people with DVT develop the condition due to one or several risk factors and underlying conditions.

Inactivity

If the human body is inactive for long periods, blood can build up in the lower limbs and pelvic area.

This situation is not a problem for most people. As soon as physical activity levels return to normal, blood flow speeds up. The vein and arteries redistribute blood around the body.

However, prolong inactivity means that blood in the legs may slow a person’s blood flow, increasing the risk of clots forming.

A person might be inactive for long periods due to a range of causes, including:

  • an extended hospital stay
  • being immobile at home
  • remaining seated during a long journey, such as a flight
  • a disability that restricts movement

Injury or surgery

An injury or surgery that damages veins can slow the flow of blood. This increases the risk of blood clots. General anesthetics can also widen the veins, making it more likely that blood pools and clots may form.

While this risk may affect anyone having major surgery, the NHLBI suggest that people receiving knee and hip surgery, particularly, have a high risk of developing DVT.

Genetics

A person may have an inherited disorder that makes blood clots more likely, such as Factor V Leiden thrombophilia.

However, even though having this condition increases the risk, only around 10% of people with it go on to develop unusual blood clots, according to Genetics Home Reference.

Pregnancy

As a fetus develops inside the uterus, pressure against a woman’s veins in the legs and pelvis increases. A woman has an increased risk of DVT during pregnancy until six weeks after delivering their baby.

Females with some inherited blood disorders, such as hereditary antithrombin disorder, have a higher risk of DVT during pregnancy compared with other women.

Cancer

Some cancers have links to a higher risk of DVT, including late stage colon, pancreatic, and breast cancers.

Cancer therapies and procedures can also increase a person’s risk of DVT, including chemotherapy, a central venous catheter, and certain cancer surgeries.

Read more about cancer and its treatments here.

Irritable bowel disease

People with irritable bowel disease (IBD) have a higher risk of DVT. A 2018 study found that the risk may be three to four times higher than that of a person without IBD.

Learn all about IBD here.

Heart problems

Any condition that affects how well the heart moves blood around the body can cause problems with clots and bleeds.

Conditions such as heart attacks or congestive heart failure may increase a person’s risk of developing a blood clot.

Find out more about heart disease here.

Hormone-based medications

Females who take hormone-based birth control or are on a course of hormone replacement therapy (HRT) for menopause have a higher risk of DVT than those who do not take these medications.

Discover everything you need to know about HRT here.

Obesity

People with obesity experience more pressure on their blood vessels, especially those in the pelvis and legs.

For this reason, they may have an increased risk of DVT.

Smoking

People who smoke tobacco regularly are more likely to develop DVT than people who have never smoked or have stopped.

People finding it difficult to quit smoking might find these tips helpful here.

Varicose veins

Varicose veins are enlarged and misshapen veins. While they often do not cause health problems, particularly overgrown varicose veins may lead to DVT unless a person receives treatment for them.

Learn more about varicose veins here.

Age

Even though DVT may develop at any age, the risk increases as a person’s age advances.

According to the NHLBI, the risk of DVT doubles every 10 years after people reach 40 years of age.

Sex

A person’s sex can affect their DVT risk.

Females are more likely than males to experience DVT around childbearing age. However, females have a lower risk after menopause than men do at the same age.

If a person suspects that they may have DVT, they should seek immediate medical attention. The doctor will ask questions about symptoms and medical history before carrying out a physical examination.

A doctor will usually not be able to diagnose DVT through symptoms alone and may recommend tests, including:

  • D-dimer test: D-dimer is a protein fragment that is present in blood after a blood clot fibrinolysis degrades a blood clot. A test result revealing more than a certain amount of D-dimer indicates a possible blood clot. However, this test may not be reliable in individuals with certain inflammatory conditions and after surgery.
  • Ultrasound: This type of scan can detect clots in veins, alterations in blood flow, and whether the clot is acute or chronic.
  • Venogram: A doctor may request this scan if the ultrasound and D-dimer tests do not provide enough information. The doctor injects a dye into a vein in the foot, knee, or groin. X-ray images can track the dye as it moves to reveal the location of a blood clot.
  • Other imaging scans: MRI and CT scans may highlight the presence of a clot. These scans may identify blood clots while testing for other health conditions.

DVT treatment aims to:

  • stop the growth of a clot
  • prevent a clot from becoming an embolism and moving into the lung
  • reduce the risk that DVT might come back after treatment
  • minimize the risk of other complications

A doctor may recommend several methods to manage DVT, as follows:

Anticoagulant medications

These are drugs that prevent the clot from growing, as well as reducing the risk of embolism. Two types of anticoagulants support the treatment of DVT: Heparin and warfarin.

Heparin has an immediate effect. For this reason, doctors usually administer it first through a brief course of injections lasting less than a week.

With warfarin, the doctor is likely to recommend a 3–6-month course of oral tablets to prevent recurrence of DVT.

People with recurrent DVT may need to take anticoagulant medication for the rest of their lives.

Thrombolysis

People with more severe DVT or PE require immediate medical attention. The doctor or emergency team administers drugs called thrombolytics, or clot busters, that break down clots.

Tissue plasminogen activator (TPA) is an example of a thrombolytic drug.

Excessive bleeding is a side effect of these drugs. As a result, medical teams only administer TPA or similar interventions in emergency situations.

Healthcare professionals administer TPA through a small catheter, or tube, directly into the site of the clot. Patients undergoing catheter-directed thrombolysis will be in the hospital for several days and have intermittent “lysis checks” to make sure the clot is breaking down appropriately.

Inferior vena cava filter

A surgeon inserts a very small device, resembling an umbrella, into the vena cava, which is a large vein. The device catches blood clots and stops them moving into the lungs while allowing blood flow to continue.

Compression stocking

People wear these to help reduce pain, limit swelling, and prevent ulcers from developing. Stockings can also protect the individual from post-thrombotic syndrome.

Someone with DVT will have to wear stockings at all times for at least 24 months.

There is no available method for screening people for DVT. However, doctors recommend three ways for people with one or several risk factors, such as recent surgery, to prevent the first occurrence of DVT.

These are:

  • Regular movement: A doctor might recommend staying highly mobile after surgery to stimulate blood flow and reduce the risk of a clot.
  • Maintaining pressure on the at-risk area: This can prevent blood pooling and clotting. Medical professionals may recommend wearing compression stockings or a boot that fills with air to increase pressure.
  • Anticoagulant medication: A doctor may prescribe blood-thinning medication to reduce the risk of clotting before or after surgery.

As smoking and obesity are also key risk factors, it may be advisable to quit smoking and engage in regular physical activity.

According to the American Heart Association (AHA), 150 minutes of moderate-to-high intensity exercise every week is the amount they recommend.