Overview
Deep vein thrombosis, or DVT, is a blood clot in one of the deep veins of the body. Most form in the calf or thigh, though a clot can also form in the pelvis or arm.
The clot blocks blood returning to the heart, so the leg swells and aches. The greater danger is that a piece breaks away and blocks an artery in the lungs, which is called and can be fatal. With prompt treatment most people recover well.
Symptoms
The signs usually affect one leg only:
- Pain, tenderness or a cramping ache, often in the calf
- Swelling of the leg, ankle or foot
- Skin that feels warm to touch
- Skin that looks red or darker than usual
About half of people with a DVT have no symptoms. Sometimes the first sign is in the chest, when part of the clot has reached the lungs.
When to see a doctor
See a doctor the same day or the next for pain or swelling in one leg, especially after surgery, bed rest, pregnancy or a long journey. A suspected DVT is usually confirmed by within a day.
Causes
Blood in the deep veins is kept moving largely by the squeeze of the leg muscles. When a person is still for a long time, the flow slows and a clot can form.
A clot is also more likely if a vein has been injured, during surgery or a fracture, or if the blood clots more readily than usual, as in a clotting disorder, cancer, pregnancy, or with medicines containing oestrogen.
Risk factors
- A hospital stay, major surgery, or a leg in a plaster cast
- Bed rest or sitting still, including journeys over four hours
- A previous clot, a family history of clots, or a clotting disorder
- Cancer and some cancer treatments
- Pregnancy and the six weeks after delivery
- Contraceptive pills and hormone therapy containing oestrogen
- Being over 60, overweight or a smoker
Complications
The most serious complication is , when part of the clot travels to the lungs. It causes sudden breathlessness, chest pain, a fast heartbeat and sometimes collapse, and is an emergency.
Later, damage to the valves inside the vein can leave a leg that aches, swells and feels heavy, with skin changes and sometimes ulcers. This is called post-thrombotic syndrome.
Prevention
- Getting up and moving as soon as it is safe after surgery or an illness
- On long journeys, walking about and doing ankle and calf exercises in the seat
- Drinking enough water and wearing loose clothing when travelling
- Keeping to a healthy weight, staying active and not smoking
- Using the clot-preventing injections or stockings offered in hospital
- Telling any doctor about a previous clot before surgery
Diagnosis
The doctor examines the leg, weighs up the risk factors and arranges tests. These usually include:
- A D-dimer blood test, which measures a substance released when a clot breaks down
- A Doppler of the leg, showing where the flow is blocked
- A of the chest if a is suspected
- Tests for clotting disorders, in selected people
Treatment
Treatment is with medicines that thin the blood, called anticoagulants. They do not dissolve the clot, but they stop it growing, let the body break it down, and greatly reduce the chance of a piece reaching the lungs. They may be tablets or injections, usually for at least a few months.
Compression stockings are sometimes advised to ease swelling, and keeping the leg raised when resting helps. A large clot that threatens the leg or the lungs may be treated with clot-dissolving medicine or removed.
While on a blood thinner, report unusual bruising or bleeding, and mention it before starting any new medicine.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Pain and swelling in the calf is just a muscle pull or weakness, and massage will loosen it.”What is true?
Fact
A clot in a deep vein can feel very like a pulled muscle. Rubbing or massaging the leg does not help and a swollen, painful leg should be examined rather than treated at home. An ultrasound scan settles the question quickly.
Myth“Only people who take long flights get a clot in the leg.”What is true?
Fact
Long journeys do raise the risk, but far more clots follow surgery, a hospital stay, a broken bone in a plaster cast, cancer, pregnancy or simply days in bed with an illness. Any long period of not moving can be enough.
Myth“A clot in the leg stays in the leg, so it is only a local problem.”What is true?
Fact
Part of the clot can break off, travel through the blood and lodge in the lungs. That is called a pulmonary embolism and it is life threatening. This is the reason a suspected clot is treated as urgent.
Myth“Once the pain settles I can stop the blood thinner.”What is true?
Fact
The leg often feels better long before the treatment is complete. Blood-thinning medicine is prescribed for a set period, usually at least a few months, to stop the clot growing and to lower the chance of another one. Stopping early should only be considered with the doctor who prescribed it.
Myth“Someone with a clot must stay in bed and not walk.”What is true?
Fact
Once treatment has begun, gentle walking is usually encouraged rather than forbidden, because movement helps the circulation. How soon and how much to walk is decided by the treating doctor, and any new breathlessness or chest pain must be reported at once.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
How is a clot in the leg different from an ordinary muscle cramp?
A cramp comes on suddenly, is short lived and settles when the muscle relaxes. A clot tends to cause a steady ache or tenderness in one leg that lasts, usually with swelling and warmth, and it often follows a period of not moving. Because the two can feel similar, a leg that stays swollen and painful should be examined.
Is it safe to fly after a DVT?
Most people can fly again once the clot has been treated and the doctor agrees, though the timing depends on the size of the clot, the treatment and any breathing symptoms. On the journey, move about when you can, do ankle exercises, drink water and wear compression stockings if they have been advised.
Will I need blood thinners for life?
Not always. When the clot follows a clear temporary cause, such as surgery or a long period in bed, a course of a few months is often enough. When there was no obvious cause, or when there have been repeated clots or an ongoing risk such as cancer or a clotting disorder, longer treatment may be advised. Your doctor will review this with you.
Can DVT happen in the arm?
Yes, though it is much less common than in the leg. It can occur around a drip or a long-term intravenous line, after injury, or with heavy repeated use of the arm. The symptoms are similar: pain, swelling, warmth and discoloration, and it should be assessed in the same way.
