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Symptoms and diagnosis of deep vein thrombosis (DVT)

Deep vein thrombosis, or DVT, doesn’t always cause any symptoms as a blood clot forms in a deep vein, often in the legs.

However, at other times there are warning signs of DVT, which require urgent medical investigation and treatment.

Signs and symptoms of DVT

Half of all DVT cases cause no symptoms. If you do have any of the DVT symptoms below - especially if they occur suddenly - seek medical advice right away:

  • Swelling in one or both legs
  • Pain or tenderness in one or both legs, which may occur only while standing or walking
  • Warmth in the skin of the affected leg
  • Red or discoloured skin in the affected leg
  • Heavy ache in the leg

If a blood clot breaks free and travels to your lungs it's called a pulmonary embolism, and it can be fatal. Pulmonary embolism may not cause symptoms, but if you ever suffer sudden coughing, which may bring up blood; sharp chest pain; rapid breathing or shortness of breath; or severe lightheadedness, call 999 or go to an accident and emergency department (A&E) immediately.

Diagnosing deep vein thrombosis

To diagnose DVT, your GP will ask about your health, medical history and symptoms, as well as conduct a physical examination. However, because DVT symptoms are shared by many other conditions, you may need one or more special tests to rule out other problems or to confirm a diagnosis. 

Tests to diagnose deep vein thrombosis may include:

  • D-dimer test. A type of blood test that detects pieces of blood clot that have broken down and are loose in the blood stream.
  • Duplex ultrasound. High-frequency sound waves bounce off the inside of your body, producing images of your blood vessels. A radiologist spreads warm gel on your skin and then moves an ultrasound wand over the area. The wand sends sound waves into your body and then sends the echoing waves to a computer, which produces images of your vessels and sometimes the blood clots, as well. Painless and non-invasive, ultrasound tests require no radiation but require a skilled person to obtain accurate results. This test is less sensitive in finding blood clots that are very deep inside the body, such as in the pelvis.
  • Venography. This test involves taking a special X-ray that allows your doctor to see the anatomy of your veins. Sometimes it also allows the doctor to see a clot, too. During the test, the doctor injects a radioactive dye into a vein on the top of your foot. This highlights the veins on the X-ray. Although accurate, this test carries a slight risk of increasing the chances of additional blood clots.
  • Magnetic resonance imaging (MRI). This test uses radio frequency waves and a strong magnetic field to create detailed images of the inside of your body. You lie still on a sliding table while the test takes place. Expect to hear loud tapping or knocking sounds. If needed, you may get a fluid injected into your vein to enhance the images of your blood vessels. This imaging test is effective at finding DVT in the pelvis, as well as in the thigh. It also allows your doctor to examine both legs at once.

If you believe you have deep vein thrombosis symptoms, don't wait. Seek medical advice right away.

WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on December 21, 2015

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