What to know about deep vein thrombosis

What to know about deep vein thrombosis

Deep vein thrombosis occurs when, usually, blood clots form in a deep leg vein. The disease can affect veins in the pelvis, in addition to leg veins.

Two aspects of the condition known as venous thromboembolism are deep vein thrombosis (DVT) and pulmonary embolism ( PE).

DVT is an urgent medical condition. The Centers for Disease Control and Prevention ( CDC) report that within one month of diagnosis, 10-30 percent of people who develop DVT in the leg encounter fatal complications.

We describe DVT in this post, clarify how to identify it, and the ways to handle it.

What is DVT?

A person with DVT may experience pain and swelling in the affected limb.
A person with DVT may experience pain and swelling in the affected limb.

DVT is blood coagulation that happens with deep veins, particularly in the leg or pelvis.

Physicians call this an embolus if the thrombus, or clot, breaks off. Emboli may make its way to the lung which causes PE.

Clots can also form in the arm’s veins, for example in people with Paget-Schoetter disease.

DVT is the most prevalent cause of maternal death in the developing world according to a 2017 study.

DVT is extremely rare in children. According to a 2016 report, the latest estimates indicate that DVT produces 0.30 in every 100,000 children under the age of 9, and 0.64 in every 100,000 children aged between 10 and 19.


Some people can experience DVT without the symptoms being identified. When symptoms may arise, however, they can mimic 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

DVT only occurs on one leg in most cases. All legs may however have DVT on rare occasions.

The following symptoms may indicate PE if a clot dislodges and travels into the lung:

  • 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 DVT’s most common problem, and can be life-threatening. This occurs when a fragment of a blood clot dislodges through the lungs and makes its way into the bloodstream.

The clot gets trapped and interferes with blood supply in one of the blood vessels in the lung. In mild PE a person may not be aware of this.

A medium sized clot can cause chest pain and breathing problems. The lung could collapse, in more serious cases. PE can cause heart failure and can result in fatalities.

Post-thrombotic syndrome

This is more common among people suffering from recurrent DVT. A person with post-thrombotic syndrome can experience the following symptoms, though they differ between individuals, according to a 2016 review:

  • 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.

Causes and risk factors

When there is no clear cause, an person can develop DVT. However, according to the National Heart , Lung, and Blood Institute (NHLBI), the disorder is acquired by most people with DVT due to one or more risk factors and underlying conditions.


Blood can build up in the lower limbs and pelvic region if the human body is inactive for long periods of time.

To most people this situation isn’t a concern. The blood flow picks up as soon as the rates of physical activity return to normal. Redistribute blood across the body across the vein and arteries.

Prolonged inactivity does, however, mean that blood in the legs can reduce a person’s blood flow, raising the risk of forming clots.

A person may be inactive for long periods because of a variety of reasons 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 causing damage to veins can slow blood flow. That increases the risk of clots in the blood. General anesthetics will also expand the veins, making the blood vessels and clots more likely to form.

Although this risk may affect anyone with major surgery, the NHLBI indicates that especially those undergoing knee and hip surgery are at high risk of developing DVT.


A person may have an inherited condition that is more likely to cause blood clots, such as thrombophilia Factor V Leiden.

While having this disorder raises the risk, according to Genetics Home Reference, only around 10 percent of people with it tend to develop irregular blood clots.


When a fetus grows inside the uterus, pressure in the legs and pelvis against a woman’s veins increases. During pregnancy a woman has an increased risk of DVT before six weeks after delivering her infant.

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


Some cancers are associated with a higher risk of DVT, including late stage colon, pancreatic cancer , and breast cancer.

Cancer treatments and procedures can also raise the risk of DVT to a person, including chemotherapy, a central venous catheter, and some cancer surgeries.

Here’s more about cancer and its therapies.

Irritable bowel disease

People with irritable bowel disease (IBD) have an increased chance of developing DVT. A 2018 report found that the risk could be three to four times greater than an IBD-free person’s.

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 menopause hormone replacement therapy course (HRT) have a greater risk of DVT relative to those who do not take such medications.

Discover everything you need to know about HRT here.


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.


Those who regularly smoke cigarettes are more likely to experience DVT compared with people who have never smoked or quit.

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

Varicose veins

The varicose veins are swollen and the nerves are deformed. Although they often cause no health problems, particularly overgrown varicose veins can lead to DVT unless a person is treated for them.


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.


A person’s sex can affect their DVT risk.

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


When a person suspects getting DVT they should seek medical attention immediately. Before conducting a physical exam, the doctor will ask questions about symptoms and medical history.

Normally a doctor may not be able to diagnose DVT from symptoms alone, and may prescribe 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

There are medications that both prevent the clot from developing and raising the risk of embolism. DVT therapy is accompanied by two types of anticoagulants: Heparin and warfarin.

It has an immediate effect on heparin. For this reason, doctors usually first administer it through a short course of injections that last less than a week.

The doctor is likely to prescribe a 3–6-month course of oral tablets with warfarin to prevent DVT from returning.

People with chronic DVT may continue to take anticoagulant drugs for the rest of their lives.


Individuals with greater frequency of DVT or PE need urgent medical attention. The doctor or emergency team administers drugs which break down clots called thrombolytics, or clot busters.

An example of a thrombolytic drug is the tissue-plasminogen activator (TPA).

Such medications have a side effect of heavy bleeding. As a result , medical teams only administer TPA or similar interventions in emergency situations.

Healthcare practitioners administer TPA directly into the clot site through a small catheter, or tube. Patients suffering from catheter-directed thrombolysis will be in hospital for several days and will undergo regular “lysis checks” to ensure that the clot breaks down properly.

Inferior vena cava filter

A surgeon puts a very small tube into the vena cava, which is a large vein, like an umbrella. The system detects blood clots and prevents them from going into the lungs while allowing for continuous blood flow.

Compression stocking

People wear these to help relieve discomfort, alleviate swelling and avoid the development of ulcers. Stockings may also protect a person against post-thrombotic syndrome.

At at least 24 months, someone with DVT would be forced to wear stockings at all times.


There’s no tool available to test people for DVT. However, doctors prescribe three ways to avoid the first incidence of DVT for individuals with one or more risk factors, such as recent surgery.

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.

Since smoking and obesity are also main risk factors, stopping smoking and engaging in regular physical activity may be advisable.

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