What a deep vein thrombosis is

A deep vein thrombosis is a blood clot in a deep vein, usually in the leg. Deep vein clots usually form in the legs, thighs or pelvis, though they can occur in any vein in the body. The legs are most affected because that is where blood pools: the sluggish flow of blood in the legs favours clot formation in the lower limbs.

Symptoms

It can cause pain, swelling, warmth and redness, but some are silent. Small clots can be silent because other veins, called collaterals, keep the blood flowing. Larger clots cause blood and fluid to pool, leading to pain and swelling over the area of the clot or even the entire limb.

Who is at risk

The risk rises after surgery, long periods of immobility, long journeys, pregnancy, hormone treatment and cancer. Risk factors are anything that makes blood clot more easily, and prolonged immobility, hormone treatments, cancer and recent surgery remain the most important.

How it is diagnosed

An ultrasound makes the diagnosis. A small probe is moved over the skin along the course of the veins, and blood flow and clots can be seen easily with this simple scan, without any radiation.

How it is treated

Treatment with blood thinners prevents the clot from growing and from travelling to the lungs, which is the real danger. Blood thinners (anticoagulants), either the older vitamin K-type tablets or the newer direct oral anticoagulants, prevent further clot from forming, while the clot itself is broken down by the body's own defences. How quickly a clot resolves varies widely with its size and any ongoing risks, from about two weeks to as long as six or seven months.

How long to continue treatment depends on why the clot formed, and it is a decision we make together. In general, treatment lasts two to six months; in some cases it is lifelong.

After a DVT

Some patients develop long term leg swelling, and compression stockings and exercise can help. This is known as post-thrombotic syndrome: the valves inside the veins are damaged, blood and fluid pool, and the leg swells, aches and the skin may discolour. Compression stockings, exercise and losing weight all help to prevent these symptoms to varying degrees.

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Frequently Asked Questions

What are the symptoms of DVT?

A deep vein thrombosis is a blood clot in a deep vein, usually in the leg. It can cause pain, swelling, warmth and redness, but some are silent.

Why is a DVT dangerous?

A clot can dislodge from the leg and travel to the vessels of the lungs, and a large clot in the lungs can be life-threatening. Treatment with blood thinners prevents the clot from growing and from travelling to the lungs.

How long does DVT treatment last?

In general, treatment lasts two to six months, and in some cases it is lifelong. Multiple factors decide the duration, and it is a decision we make together.