Deep Vein Thrombosis

Deep vein thrombosis is a blood clot that forms in one of the deep veins of the body, usually in the calf or thigh. Veins carry blood back to the heart, and when a clot partly or fully blocks a deep vein it can slow this flow and cause swelling and pain in the affected limb.

DVT matters not only because of discomfort in the leg but because of what can happen if part of the clot breaks away. It can travel through the bloodstream to the lungs, where it is called a pulmonary embolism. For this reason DVT is taken seriously and treated promptly.

DVT usually affects one leg and can cause throbbing or cramping pain, often in the calf or thigh, along with swelling, warmth and skin that looks red or darker than usual. The area may feel tender, and the swelling does not ease when you rest or raise the leg. Some people have no obvious symptoms at all.

Sudden breathlessness, sharp chest pain that may be worse when breathing in, a fast heartbeat, coughing up blood or feeling faint can be signs that a clot has travelled to the lungs. This is a medical emergency and needs immediate help.

Clots are more likely to form when blood flow slows or when blood clots more easily than normal. Risk is higher during long periods of immobility, such as after major surgery, a hospital stay, a serious injury, or a long journey, and during and after pregnancy.

Other things that increase the risk include being older, being overweight, smoking, some types of cancer and their treatment, certain hormone medicines such as the combined contraceptive pill or hormone replacement therapy, and inherited conditions that make the blood more likely to clot. A previous DVT also raises the risk of another.

If DVT is suspected, a clinician will ask about your symptoms and risk factors and examine the affected leg. A blood test called a D-dimer can help judge how likely a clot is, although it is not specific on its own.

The main test to confirm DVT is an ultrasound scan of the leg, which uses sound waves to look at blood flow in the deep veins and can show whether a clot is present. Occasionally other imaging is used. If a pulmonary embolism is suspected, scans of the chest may be arranged urgently.

The main treatment is blood-thinning medicine, called an anticoagulant, which stops the clot getting bigger and reduces the chance of a piece breaking off or new clots forming. Several types are available, and treatment is usually continued for at least a few months; some people need it for longer depending on the cause and their risk of recurrence.

Staying active as advised, raising the leg when resting and sometimes wearing compression stockings can help with swelling and discomfort. In certain situations other treatments may be considered. It is important to take anticoagulants exactly as prescribed and to attend follow-up, because both clotting and bleeding need to be balanced carefully.

The risk of DVT can be lowered by staying active, moving and stretching your legs during long periods of sitting or travel, keeping to a healthy weight and not smoking. Around surgery or a hospital stay, measures such as early movement, special stockings or short-term blood thinners are often used to reduce the risk.

Most people recover well with treatment, although some are left with longer-term leg swelling, aching or skin changes known as post-thrombotic syndrome. Because a previous clot raises the risk of another, it is important to be aware of the warning signs and to follow advice about prevention and any ongoing treatment.