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Deep vein thrombosis (DVT)


Expert reviewer, Dr Shankara Paneesha, Consultant Haematologist
Next review due September 2020

Deep vein thrombosis (DVT) is a condition in which a blood clot forms in one of your deep veins. This is usually in one of the large veins in your leg. You can also get DVT in your pelvis or your abdomen.

DVT causes pain and swelling. If the blood clot moves and travels to your lungs, it can lead to a pulmonary embolism, which can be life-threatening. Every year in the UK, about one in 1,000 people get a DVT.

Symptoms of deep vein thrombosis

Most people with DVT won’t have any symptoms. If you do have symptoms, they can vary from mild to severe and can affect any part of either leg.

If you have a blood clot that is large and mostly or totally blocks your vein, you may have some symptoms. These include:

  • a swollen leg
  • pain and tenderness along the line where your vein is
  • warm skin that looks red

These can often be symptoms of other conditions too. In fact, only about one in three people with a swollen and painful leg will have DVT. If you have any of these symptoms, contact your GP as soon as possible.

Diagnosis of deep vein thrombosis

Your GP will ask about your symptoms and medical history, and examine you. They’ll make an assessment of how likely you are to have a DVT, based on all your symptoms and risk factors. If your GP thinks a DVT is likely, they’ll refer you for some tests to confirm the diagnosis. These may include the following.

  • A blood test called a D-dimer. This measures a substance called fibrin, which develops in your body when a blood clot breaks down. The test is usually used to rule out DVT as the cause of your symptoms. D-dimer tests may be positive or raised if you have other health conditions such as cancer, or after an operation.
  • A leg vein ultrasound. This uses sound waves to look at your blood as it flows through the blood vessels in your leg.

Treatment of deep vein thrombosis

Treatment for DVT aims to stop the blood clot in your vein progressing and getting worse. It also aims to reduce your likelihood of developing complications from DVT, and your risk of getting another DVT.

Anticoagulants

The main treatment for DVT is a type of medicine called an anticoagulant. Anticoagulants prevent blood clots forming or stop blood clots getting bigger.

If your doctor suspects you have a DVT, you’ll usually start treatment with an anticoagulant before your diagnosis is even confirmed. Which type of anticoagulant your doctor recommends will depend on your general health and what caused your DVT, as well as local guidelines and your doctor’s own experience. You can usually receive treatment through your GP or as an outpatient at your local hospital. But you may need to be admitted to hospital for treatment if you have any complications, or if you’re at increased risk of bleeding.

The two main types of anticoagulant used for DVT are:

  • novel anticoagulants (NOACs)
  • heparin (injections) and warfarin

Your doctor may recommend trying an NOAC first. NOACs include rivaroxaban, dabigatran, apixaban and edoxaban. These medicines have the advantage that you don’t need heparin injections with them, and you don’t need to be monitored as closely as with older anticoagulants. If you have certain health conditions, an increased risk of bleeding or are pregnant, you may not be able to have NOACs.

If you’re unable to have treatment with an NOAC for any reason, you’ll usually be offered treatment with low-molecular weight heparin (LMWH) and warfarin. LMWH is given as an injection under your skin, while warfarin is taken as tablets. You’ll need to have both treatments to begin with, because it takes a few days for the warfarin to start to work. You’ll be able to stop the LMWH after around 5 days. But you’ll probably need to continue taking the warfarin tablets for three to six months, sometimes longer.

If you have kidney failure or you’re at high risk of bleeding, you may need treatment with another type of heparin – called unfractionated heparin. You’ll need to go into hospital to have this, where doctors will be able to monitor you.

You’ll need to have regular blood tests if you’re taking warfarin, to make sure your blood is clotting properly. This is called an INR test. You won’t need to be monitored in this way if you’re taking an NOAC.

If you’re taking an anticoagulant, your nurse or doctor should give you an alert card, which you should always carry with you. If you’re taking warfarin, you should also be given an anticoagulant information booklet.

If your symptoms get worse when you begin taking anticoagulants or if you develop another DVT, your doctor may try switching you to an alternative treatment.

Inferior vena cava filters

Most people with DVT can have treatment with anticoagulants. But if you can’t for any reason, your doctor may suggest you try treatment with a device called an inferior vena cava (IVC) filter. An IVC filter is a small metal device placed inside a vein to trap any clots before they can travel to your heart and lungs. You may also have one if you have recurrent DVT (it keeps coming back).

Ongoing treatment

Your doctor is likely to advise you to try to start walking as soon as possible after having a DVT. It’s safe to get up and about (it won’t cause the clot to move) and it can help to ease your symptoms.

Your doctor may suggest you wear a compression stocking on the affected leg for up to two years afterwards. These are tight stockings that help to pump your blood through your legs. They can help to reduce any ongoing symptoms you have, and they’re thought to reduce your risk of developing post-thrombotic syndrome (see Complications for more information). The stockings come in different sizes. You should have them replaced every three to six months and have your leg measured each time you get new stockings. Compression stockings aren’t advised for everyone who has had a DVT.

Depending on your medical history and why you developed a DVT, your doctor may recommend you continue taking anticoagulant medicines for the long term. This is to prevent any more blood clots developing.

Causes of deep vein thrombosis

For as many as half of all people who get a DVT, there is no specific cause. But developing DVT while you’re in hospital, or in the three months after you leave hospital, is common.

There are certain things that are known to be associated with developing DVT. These include:

  • being inactive for long periods of time; for example, if you’re recovering after a big operation or are sitting still during a long journey
  • having blood that clots more easily; for instance, if you’re pregnant, have certain conditions that affect your blood clotting, or you’re taking the contraceptive pill
  • having cancer
  • if your blood vessels have been damaged from an injury or operation

You’re also at greater risk of developing a DVT if:

  • you’ve had DVT before
  • you're over 60
  • you’re a smoker
  • you’ve very overweight (obese)
  • you’re dehydrated (not getting enough fluid)
  • you have a severe infection

Travel risks

If you travel long distances and spend hours sitting down, then you could be more likely to develop deep vein thrombosis.

Any kind of long distance travel (plane, car, coach or train) increases your risk of DVT by about three times, but the risk is still a small one. For example, for flights that last 16 hours or more, there will be one person who develops DVT or pulmonary embolism every 1200 flights. The longer the journey, the greater your chances of getting a blood clot.

Complications of deep vein thrombosis

Most of the time, deep vein thrombosis (DVT) doesn’t cause any further problems. However, possible complications of DVT can include the following.

Pulmonary embolism

A pulmonary embolism happens when a blood vessel in your lungs becomes blocked. A piece of the blood clot in your leg can break off and travel through your body in your bloodstream until it gets to your lungs, where it gets stuck. If blood isn’t reaching your lungs properly, it can be very serious. Getting treatment quickly can be life-saving.

Post-thrombotic syndrome

This is when you have ongoing symptoms after a DVT, such as a painful and swollen leg and red, dry skin. It can happen if the damage caused by DVT increases the pressure in your vein. If the condition becomes severe, you could develop an ulcer on your leg and this can be difficult to heal. Wearing compression stockings may help to prevent post-thrombotic syndrome.

Prevention of deep vein thrombosis

If you're in hospital for a big operation or because of illness, you may be more likely to develop deep vein thrombosis or pulmonary embolism. When you’re in hospital, your nurse or doctor will measure your risk of developing a blood clot. You may be asked to do the following to reduce your risk.

  • Drink plenty of fluids. If you can’t drink, you’ll be given fluids through a drip.
  • Get up and start moving about as soon as you can after an operation or illness.
  • Wear compression stockings to help your circulation.
  • Have an injection of an anti-clotting medicine such as enoxaparin or tinzaparin or daltaparin as well as or instead of wearing compression stockings.
  • Use an intermittent pneumatic compression device. This is an inflatable cuff wrapped around your leg or foot and an electrical pump that inflates it, squeezing your deep veins.

You can also prevent blood clots from developing when you’re sitting down a lot during a long journey by doing the following.

  • Get up and walk around whenever you can.
  • Do leg exercises in your seat, for example, bend and straighten your knees, feet and toes every half hour.
  • Drink enough fluid so you don’t become dehydrated.
  • Drink non-alcoholic drinks and avoid caffeine.

Frequently asked questions

  • Anticoagulant medicines stop blood clotting. There are several different ones, including warfarin and newer medicines such as apixaban and dabigatran. Because they affect the way your blood clots, the main side-effect is bleeding.

    If you’re taking warfarin, you’ll need to have regular blood tests to make sure your blood is clotting properly. This blood test is called an INR test. There are several things that can affect how well warfarin works – including other medicines you may be taking, if you lose or gain weight or if you’re ill. Having the INR test can help your doctor to make sure you’re getting the right amount of medicine and adjust it if necessary. You won’t need INR tests if you’re taking the newer anticoagulants (NOACs), as you won’t need to change the amount you’re taking.

    If you’re taking warfarin, your nurse or doctor should also give you an anticoagulant information booklet and an alert card, which you should always carry with you. The card lets other health professionals know that you’re taking warfarin in case of an emergency or before you have any other treatment.

    You can lower the likelihood of any bleeding as a side-effect by:

    • taking the medicines at the same time every day
    • telling your doctor about any bruising straightaway
    • telling any doctor or your dentist that you take an anticoagulant before you start any treatment
    • using paracetamol for pain relief instead of aspirin or non-steroidal anti-inflammatory drugs
  • About one in every three people who develop DVT that seems to have no definite cause, will have another one within five years. If you developed DVT after an injury or operation, then your chances of having another one are less – about one in every seven people.

    If there is a high chance that you may develop another DVT, your doctor will probably ask you to keep taking anticoagulant medicines for the long term. This could be for years. Your doctor will do regular blood tests to check how your blood is clotting, and may change your treatment depending on the results.


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Related information

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  • Reviewed by Pippa Coulter, Specialist Health Editor, Health Content Team, September 2017
    Expert reviewer, Dr Shankara Paneesha, Consultant Haematologist
    Next review due September 2020



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