DVT occurs commonly in the calves of the legs, but can also happen in the thigh or other parts of the body, such as the arm. DVTs are normally small so your body can break them down without your needing to visit hospital for treatment. DVT can sometimes lead to more serious complications, however.

The clotting mechanism of our bodies protects us from severe loss of blood when a vein or artery is injured. As a result, blood can sometimes form a clot inside a blood vessel, which is called a venous thrombosis. If a blood clot forms in an artery, it is called an arterial thrombosis. DVT is a type of venous thrombosis.

How does DVT happen?

There are two types of veins in our legs - deep veins that carry most of the blood up the legs toward the heart, and superficial veins, which you can see just under the skin (these can become varicose veins).

Blood normally flows smoothly through these veins without clotting. In some people, though, DVT clots can be triggered by a combination of factors.

For example, long periods of inactivity ⁽¹⁾ can cause DVT. The deep veins in your legs lie between layers of muscles, so when you're walking, running or even doing simple leg exercises, the muscles move, which helps to pump the blood up the deep veins to the heart.

When does DVT happen?

If you are immobile for a long period of time, perhaps after surgery, illness, or an accident, during a long-distance journey or even sitting at a computer for hours on end, the flow of blood in the deep veins becomes much slower. These situations can lead to DVT in some cases.

"Sticky" blood is often cited as a cause of DVT, which means that changes in the clotting mechanism of the blood have occurred and have made the blood cells stickier. This can happen during pregnancy, as you enter old age, during some drug treatments or you may even have an inherited tendency to clot.

Damage to the walls of blood vessels after surgical procedures, trauma or inflammation, can trigger blood cells to stick to the lining in an attempt to mend it. This can occur after surgical procedures, trauma or inflammation.

What are the chances of getting DVT?

DVT occurs in between one and three people ⁽²⁾ in every 1000 people in the general population every year.

DVT is more likely to occur in:

• People aged over the age of 40 ⁽²⁾
• People with a family history of blood clots
• People suffering from, or who have had treatment for cancer
• People with certain blood diseases (sickle cell anaemia)
• People being treated for heart failure and circulation problems (often caused by smoking)
• People who have had recent surgery especially on the hips or knees
• People who have an inherited clotting disorder
• People who are very tall

DVT is also more common in women:

• who are pregnant
• who have recently had a baby
• who are taking the contraceptive pill
• who are on hormone replacement therapy (HRT)

How do I recognise DVT?

DVT is often a 'silent' medical condition with no obvious signs or symptoms. It can also be confused with less serious conditions, such as a pulled or sore leg muscle.

If a DVT is associated with a long-distance journey, symptoms may develop hours or even days or weeks later.

Common DVT symptoms:

• Swelling, tenderness and pain in one leg (normally the calf). DVT rarely affects both legs
• Discolouration of the leg to a pale blue or reddish purple colour
• If DVT is in the veins in the thigh, (for example during pregnancy) the whole leg may look swollen

What are the complications of DVT?

Pulmonary embolism is a rare but potentially life-threatening complication of DVT. This can develop when part or all of the blood clot in the deep vein breaks off from the site where it was created and travels through the veins to the heart and lungs.

If this happens, the clot can block the blood supply to part of the lung, which causes the lung to collapse and can lead to heart failure.

DVT symptoms can include:

• Shortness of breath - this can be gradual, or sudden and severe
• A sharp chest pain which can be worse on breathing in
• Dizziness due to low blood pressure
• Coughing up small amounts of blood
• Rapid heartbeat
• Sudden collapse

Up to one in ten people ⁽³⁾ who suffer a pulmonary embolism will die, if they aren't treated.

Post-thrombotic syndrome (PTS)

PTS is triggered by damaged caused to the leg by DVT. Symptoms can include limb swelling, pain, skin discolouration and ulcers. The likelihood of PTS can be reduced with specialist-fitted compression hosiery which can be discussed with your medical support team.

What should I do if I think I have DVT?

DVT needs urgent medical attention and treatment. You should see your GP as soon as possible, or go straight to your nearest Accident and Emergency department.

How is DVT diagnosed?

DVT is normally diagnosed by examination and assessment of the leg and the following tests:

• A specialised blood test called a D-dimer test ⁽⁴⁾ may be used to detect pieces of a blood clot that are travelling in your blood stream
• An ultrasound scan may be used to detect a clot in the vein of your leg. A special type of ultrasound, known as Doppler ultrasound, is also sometimes used to find out how fast the blood is flowing through a blood vessel
• A venogram ⁽⁴⁾ may be used to confirm results. A contrast dye is injected into the vein in your leg and an X-ray is then used to see if the dye can flow freely through your vein or if it is being blocked by a blood clot

What is the treatment for DVT?

DVT is normally treated with anticoagulant or blood-thinning medication. Usually, treatment starts with low molecular weight Heparin, which is given as a daily injection under the skin for three to five days.

Treatment is then changed to Warfarin which is given in tablet form. Warfarin needs a few days to take effect, which is why Heparin (a faster-acting drug) is given initially.

Anticoagulants don't break down the existing clot (this is reabsorbed naturally over a period of weeks), but they prevent it from becoming larger and travelling to other parts of the body. They also prevent further clots from forming.

Each person responds differently to Warfarin, so a blood test called an INR (International Normalised Ratio) will be given to measure the clotting time of your blood. This then informs your doctor the correct dose of Warfarin for you.

For the first few weeks, your INR will probably be checked twice weekly. The treatment will normally be give from three to six months.

What are the side effects?

Both anticoagulants used in the treatment of DVT can increase the risk of bleeding.

Contact your GP immediately or seek urgent medical advice if you get any of these symptoms:

• Blood in your bowel motions or urine
• Coughing or vomiting blood
• Heavy or persistent nosebleeds
• Unexplained bruising

Some people suffer from allergic reactions to the drugs - such as difficulty in breathing, skin rash or itching. You should check the labels on your medication, if you think you are having an allergic reaction. If you think you are, you should seek medical advice immediately.

I have been told I have DVT - what can I do to reduce the pain and swelling in my leg?

• When you are sitting, keep your leg raised
• Take gentle exercise (such as walking or swimming)
• Don't stand or remain seated for long periods of time
• Wear graduated compression stockings as instructed by your clinician

What are compression stockings?

These are elasticated stockings which work by applying pressure on the skin and tissues and provide support for the veins. They can improve blood flow, reduce swelling, reduce pain and prevent leg ulcers.

Compression stockings come in a range of sizes and your legs need to be measured by a specialist to ensure you have the right fitting. Your medical team will advice you on the type of compression stockings suitable for your individual case.

My GP says I'm at high risk of DVT - how can I reduce the risk?

• If you smoke - stop
• Cut down on the amount of salt in your diet
• Eat a balanced (and reduced fat) diet with at least five portions of fruit and vegetables per day
• Increase your physical activity
• When sitting, don't cross your legs
• Cut down on alcohol

I'm going on a long-haul flight. What can I do to protect myself?

• Walk up and down the aisle when possible
• Contract the buttocks and abdominal muscles to stimulate circulation in the pelvis
• Stretch your arms above your head

• Drink plenty of water
• Try not to sit in a cramped position for hours
• Stretch your legs out and rotate your ankles, flexing and pointing the feet

Seek medical advice before flying long-haul if:

• You have ever had a stroke
• You have had a DVT or PE before
• You have a family history of clotting conditions
• You have undergone major surgery in the last three months
• You have had a hip or knee replacement within the last three months

Infolinks:

• DVT Safety Zone