Definition and Overview

Deep venous thrombosis (DVT) is a medical condition characterised by the formation of blood clots in one of the deep veins in the body. It most commonly occurs in the legs and often causes symptoms, such as leg pain and swelling.

DVT is a highly prevalent medical condition that affects hundreds of thousands of individuals each year. Early detection and treatment play a key role in preventing potentially fatal complications. One of which is pulmonary embolism, a life-threatening condition that occurs when blood clots in the veins break loose and travel towards the lungs. This puts the patient at risk of blood flow obstruction. This complication occurs in up to a quarter of all DVT cases and is a leading cause of preventable deaths in many countries.

Both deep venous thrombosis and pulmonary embolism are manifestations of venous thromboembolism (VTE), a peripheral venous disease.

Causes of Condition

One of the primary risk factors for developing deep venous thrombosis are blood-clotting disorders, which affect the way the blood clots. These disorders, which are commonly inherited, do not cause DVT on their own but may increase the risk for the condition when combined with other risk factors, such as injury or surgery.

Blood clots can also form due to prolonged lack of movement, which is common in patients confined to bed for a long time, such as those who are severely injured, have undergone extensive surgery, and suffer from prolonged paralysis. The lack of movement results in a lack of muscle contractions, which prevents blood from circulating properly.

Other risk factors for deep vein thrombosis include:

  • Pregnancy

  • Hormone replacement therapy

  • Oral contraceptives

  • Obesity or being overweight

  • Smoking

  • Cancer

  • Heart failure

  • Inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis - These are mainly associated with recurrent thromboembolisms.

  • Activities or occupations that require long periods of sitting, such as driving or flying

  • Gender - The condition is more common in men than women.

  • Age - People over 60, particularly those with a family history of DVT or pulmonary embolism, are also considered at risk.

There are also some genetic factors that can potentially cause DVT. These include:

  • Genetic mutations of the factor V Leiden

  • Deficiencies in antithrombin, protein C, and protein S

Key Symptoms

The primary symptoms of deep venous thrombosis include swelling in the affected leg. Although it is possible for the patient to experience swelling in both legs, this is quite rare.

Aside from swelling, patients can also experience:

  • Pain in the affected leg - This symptom affects more than 50% of DVT patients.

  • Leg tenderness - This symptom is observed in up to 75% of DVT patients.

  • Redness

  • Discolouration

  • Erythema or the feeling of warmth in the area where the clot formed

If the condition has caused pulmonary embolism, symptoms will include:

  • Chest pain

  • Coughing up blood

  • Dizziness

  • Fainting

  • Lightheadedness

  • Rapid pulse

  • Shortness of breath

Another potential complication of deep venous thrombosis is post-phlebitic syndrome or post-thrombotic syndrome. This occurs when the blood clot causes damage to the affected veins, resulting in oedema or persistent swelling, skin discolouration, and skin sores.

Who to See and Types of Treatments Available

Diagnosis of suspected deep vein thrombosis is performed with the help of the following tests:

  • Ultrasound

  • Blood tests

  • Venography

  • Computed tomography (CT) scan

  • Magnetic resonance imaging (MRI)

In most cases, an ultrasound can confirm a DVT diagnosis, so there is often no need to undergo more invasive tests.

While it is possible for deep venous thrombosis to resolve spontaneously without causing serious complications, it is best for patients to seek medical attention immediately after noticing symptoms. The goal of DVT treatment is to prevent the blood clot from growing and breaking loose. This is possible with:

  • Blood thinning medications - Also called blood thinners or anticoagulants, these drugs can be taken orally or intravenously. These do not break up existing clots but can keep them from getting bigger.

  • Clot busters - These medications work by breaking up existing clots. Also known as thrombolytics, they are injected directly into the clot or affected vein.

  • Compression stockings - These are worn on the affected legs to help reduce swelling. The increased pressure in the leg reduces the risk of blood pooling and prevents further growth of existing blood clots.

  • Filters - A filter works by preventing clots from breaking loose and lodging in the lungs. They are inserted into the vena cava (a large vein) in the abdomen.

There are also endovascular and surgical interventions that can be performed in case the patient does not respond well to medications and nonsurgical therapies. These include:

  • Catheter-directed thrombolysis for thrombus removal

  • Angioplasty

  • Venous obstruction stenting

  • Mechanical thrombectomy

Following treatment, patients are usually advised to take blood thinners for three months or even longer to prevent recurrences.


  • Kesieme E, Kesieme C, Jebbin N, Irekpita E, Dongo A. “Deep vein thrombosis: a clinical review.” J Blood Med. 2011; 2: 59-69.

  • Thompson AE. “Deep Vein Thrombosis.” JAMA. 2015; 313(20): 2090.

  • Bates SM, Ginsberg JS. “Treatment of Deep-Vein Thrombosis.” N Engl J Med. 2004; 351:268-277.

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