Deep Vein Thrombosis

Family Health Diary

What is a deep vein thrombosis?

The clot causes swelling of the vein or thrombophlebitis and can cause pain, aching or discomfort. This is NOT the same as a superficial clot in the leg, which is felt as a painful, often hard lump in the veins you can see on your leg. Although these cause more discomfort than a DVT, they do not cause the same complications as a DVT.

What causes deep vein thrombosis?

Clotting is part of the body’s natural healing process to plug a gap in a damaged blood vessel and prevent bleeding, but it cannot happen if blood is flowing normally. Veins carry blood from the tissues and organs of your body back to the heart to be pumped to the lungs for more oxygen. This means that blood from the lower parts of your body must travel uphill when you are standing or sitting. It is pumped from the legs by the leg muscles squeezing on the veins when the muscles are used. One-way valves in the veins prevent backward flow. If the blood flow is slow and blood pools, a blood clot can form. This can happen when you’re immobile for long periods, such as being wheelchair-bound, sitting in an office chair, plane or a car for several hours without moving your legs. Reduced cabin pressure when flying also causes fluid to move out of the blood into the surrounding tissues (oedema), which is why you may get swollen ankles, but it also ‘thickens’ the blood adding to the risk of a clot forming.

What are the symptoms?

Often there are no symptoms; those that do occur include:

  • Aching and cramps in the leg muscles
  • Pain, swelling, tenderness and redness in one area, usually the calf
  • Mild fever.

Risk factors

  • Increasing age, usually 40+
  • Contraceptive pill or hormone replacement therapy, containing oestrogen
  • Circulation problems or heart failure
  • Recent surgery, especially to a leg
  • Obesity
  • Smoking
  • Family history including inherited clotting problems
  • Long-term immobility
  • Varicose veins.


A DVT is not usually a problem on its own. However, if the clot breaks free and travels round in the blood it can become lodged in the lungs, heart or brain which can be life threatening, particularly if it happens in the lung. A blood clot in the lung is called a ‘pulmonary embolism’ and can happen several days after the DVT has formed.

Prevention and treatment

1. Seek medical advice
If you have multiple risk factors (as above), including planning a long journey, visit your medical practitioner for advice. You may be offered:

  • Heparin – for people with particular risk of DVT before long-haul travel. Heparin is an anti-coagulant and comes as an injection.
  • Compression stockings – support the lower legs and help blood get back to the heart, while increasing pressure to the legs and reducing the risk of oedema. There are different types and sizes so it is important that you are given the right ones and that they are fitted properly.

2. How to prevent a DVT

  • Keep active and take regular exercise; if you are wheelchair-bound or wearing a cast on your leg, seek help to mobilise the legs.
  • Get up from your office chair and walk around.
  • If you are travelling on a long-haul flight, make sure you exercise your legs at regular intervals and follow procedures recommended by the airline.
  • Keep hydrated by drinking lots of water and cut back on caffeine and alcohol which cause dehydration.

3. Confirmation of a clot
If you suspect you have a DVT, seek medical attention immediately. A doctor can assess the likelihood of you having a DVT and will usually do tests such as:

  • Blood test – to look for chemicals that are present in the blood after clotting
  • Ultrasound scan – to detect a clot
  • Venography – injecting a dye into the vein to show it up more clearly using X-ray.

4. Medication

  • Anticoagulants – ‘thin’ the blood and prevent more clots forming by blocking the clotting process. Heparin is given by injection into a vein and is fast-acting. Warfarin is given in tablet form and takes a few days to work.
  • Thrombolytic medication – breaks up the clot and dissolves it; because of high risk of bleeding, it is only given in extreme cases.
  • Surgery – is a last resort to remove a blood clot if other methods fail.

5. Be vigilant for further complications
There is a chance that valves in the vein where a DVT has formed may be damaged, causing varicose veins, leg ulcers or persistent leg swelling.

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