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Deep vein thrombosis (DVT)

What is deep vein thrombosis (DVT)?

Deep vein thrombosis (DVT) is a blood clot in one of the body's deep veins, usually in the legs.

It is a type of venous thromboembolism that affects around 1 in 1,000 people in the UK each year.

Signs and symptoms of DVT

Deep vein thrombosis (DVT) doesn’t always cause any symptoms as a blood clot forms. Around half of all DVT cases cause no symptoms.

If you do have any of the warning signs below - especially if they occur suddenly - seek medical advice right away:

  • Swelling in one or both legs
  • Leg 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, which can be fatal. Pulmonary embolism may not cause symptoms, but if you ever suffer from the following symptoms, call 999 or go to an accident and emergency department (A&E) immediately:

  • Sudden coughing with blood
  • Sharp chest pain
  • Rapid breathing or shortness of breath
  • Severe lightheadedness

Risk factors and causes of DVT

In some cases, the cause of DVT is unclear, but known risk factors may increase the chance of DVT occurring including:

  • Being inactive or restricted mobility - Blood can collect in the legs and lower part of your body during periods of inactivity. After long periods of time being inactive, blood flow can be slow enough for a blood clot to form. Reasons for inactivity include long journeys, such as air travel or a stay in hospital after an operation.
  • Pregnancy - Around 1 in 1,000 women experience DVT in pregnancy. This is because one of the changes to the body in preparing for giving birth is the blood clotting more easily. During pregnancy, ask your GP what you can do to help prevent DVT.
  • Oral contraceptive pill or HRT - Oestrogen hormone treatments, such as the contraceptive pill and hormone replacement therapy (HRT) cause the blood to clot more easily, increasing the risk of DVT. Progestogen-only contraceptive pills do not carry this risk.
  • Damaged blood vessels - Damage to blood vessels may occur after suffering a broken bone or muscle damage or as a side effect of medical conditions like varicose veins or chemotherapy cancer treatment. Damaged blood vessels may be narrower or blocked, which increases the risk of a clot and DVT.
  • Various medical conditions - A person may be at a higher risk of developing DVT if they have conditions including cancer, heart disease, lung disease, hepatitis, rheumatoid arthritis, the blood clotting disorder thrombophilia and the sticky blood condition Hughes syndrome.
  • Family History - A person may be at a greater risk of DVT if there is a close family history of the condition.
  • Obesity – Being overweight or obese increases a person's chance of developing dangerous blood clots. Excess body fat may affect blood flow, making clots more likely. Some experts suggest the DVT risk with obesity is at least twice that of a healthy weight person.
  • Dehydration – not drinking enough fluids can cause dehydration, which increases DVT risk. Make sure you have enough non-alcoholic drinks when you are not moving around much, such as on planes.
  • Smoking – is known to be generally bad for health but it can contribute to poor circulation and blocked or narrowed arteries, which contribute to DVT risks.

WebMD Medical Reference

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