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Deep vein thrombosisPublished by BUPA's health information team, healthinfo@bupa.com, August 2007. This factsheet is for people who have deep vein thrombosis (DVT), or who would like information about it. DVT is a condition where a blood clot forms in a deep vein, usually in the leg. DVT can cause pain and may lead to complications such as pulmonary embolism.
Deep vein thrombosis animation What is DVT?DVT happens when a blood clot forms in a deep vein. It most commonly happens in the deep veins of the lower leg (calf), and can spread up to the deep veins in the thigh. Rarely, it can develop in other deep veins, for example in the arm. Deep veins pass through the centre of the leg and are surrounded by a layer of muscle (see illustration). Blood clots that form in the superficial veins, which lie just under the skin, are known as superficial phlebitis. These superficial blood clots are different to DVT and are much less serious.
SymptomsMany blood clots that occur in DVT are small and don't cause any symptoms. Your body will usually be able to gradually break them down with no long-term effects. Larger clots may block the blood flow in the vein and cause symptoms such as:
Although not necessarily a result of DVT, if you have these symptoms you should visit your GP. ComplicationsDVT may not cause any further problems, but possible complications include the following. Pulmonary embolismThis is the most serious complication of DVT. A pulmonary embolism (PE) happens when a piece of the blood clot from a DVT breaks off and travels through the bloodstream to the lungs. In the lungs it can block a pulmonary artery. This can cause chest pain, shortness of breath or coughing up phlegm tinged with blood. In severe cases it can be fatal. PE can happen hours or even days after the DVT has formed, and may occur when there have been no obvious signs of a DVT. You should seek emergency medical treatment if you have symptoms of PE. Post-thrombotic syndromeThis happens if DVT damages the valves in the deep veins, so that instead of flowing upwards, the blood pools in the lower leg. This can eventually lead to long-term pain, swelling and, in severe cases, ulcers on the leg. Limb ischaemiaThis is a rare complication that only happens in severe DVT. Because of the blood clot in the leg vein, the pressure in the vein can become very high. This can obstruct the blood flow through the arteries, so less oxygen is carried to the affected leg. CausesYou are more likely to get DVT if you are over 40, are very tall and/or if you are obese. If you are immobile, for example after having an operation or travelling on a long-haul flight, you also have a greater risk of getting DVT. There are a number of other risk factors that make you more likely to have DVT - these include if you have:
The risk of DVT is also increased in women who:
Travel risksThere is evidence that long-haul flights (flight lasting four hours or more) may increase the risk of developing DVT. The risk is mainly the result of prolonged immobility, which can happen during any form of long distance travel, whether by car, bus, train or air. It's difficult to say from research studies whether the actual travelling directly causes the DVT, or whether the people who had DVT were at risk for other reasons. Generally your risk of developing DVT when travelling is very small unless you have one or more risk factors (such as a history of DVT, cancer or inherited thrombophilia). If this is the case, you should seek medical advice before travelling on a flight of more than three hours. You should also seek advice if you have recently had a hip or knee replacement operation, as ideally you should postpone long-haul travel for three months after surgery. DiagnosisYour GP will ask you about your medical history and examine you. He or she may refer you to a specialist for a:
TreatmentMedicinesAnticoagulant medicines such as heparin and warfarin are the most common treatments for DVT. They alter chemicals in your blood to stop clots forming so easily. There are several precautions if you are taking anticoagulant medicines.
Thrombolytic medicines work by dissolving blood clots. They carry a risk of causing bleeding, so are used rarely, and only for treating severe DVT. Compression stockingsThese are also known as graduated compression stockings. Your doctor may recommend that you use these to relieve pain and swelling, and to prevent post-thrombotic syndrome. You may need to wear them for two years or more after having a DVT. PreventionYou should ask your doctor for advice if you have risk factors for developing a DVT. You may also want to consider measures you can take to reduce the risk. This could include exercising your legs regularly, for example take a brisk 30 minute walk every day. There is no good evidence that taking aspirin reduces the risk of developing DVT. If you are having surgerySurgery and some medical treatments can increase the risk of having a DVT. So, if you are going to hospital for an operation, you may have a pre-operative risk assessment for DVT. This takes into account your personal risk factors and the type of surgery you are having. Various measures can then be used to keep your risk as low as possible. These include anticoagulant medicines and compression stockings. If you are travellingAlthough the added risk of developing DVT on a long journey seems to be low, there are some preventive measures you can take. Wherever possible, you should:
If your doctor says you are at high risk of DVT (for example if you have a previous history of DVT or a type of blood clotting disorder called inherited thrombophilia), you may need heparin injections as well as the above measures for journeys longer than four hours. Your GP or a haematologist will advise you. You should seek urgent medical advice if you develop swelling or pain in your calf or thigh, or if you have breathing problems or chest pain after travelling. Further information
Sources
Related topicsThis information was published by BUPA's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr John Houghton, FRCP FRCPath, Consultant Haematologist, Salford Royal NHS Foundation Trust, and by BUPA doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional. Publication date: August 2007. Expected review date: August 2009.
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