Dear Doc

My doctor thinks I may have thrombosis as my left leg is swollen and hurts and my veins are enlarged. I’ve had a scan, this showed nothing, but they did my upper leg, not lower and I'm waiting for my bloods to be screened. Could I have thrombosis and what are the treatment options? I haven't banged my leg or been on a flight.
Geezer, 14

It’s very unusual for someone of your age to have a thrombosis. Girls who take the contraceptive pill, or who are pregnant, run a slightly higher risk of developing thrombosis but it’s really rare in boys.

Hopefully your GP will have referred you to a hospital doctor who specialises in children’s blood conditions (a paediatric haematologist). If you haven’t been referred, it would be a good idea to ask for this.

The specialist will be able to carry out some tests to try to establish exactly what the problem is, and to rule out any underlying cause.

What is thrombosis?

A thrombosis in the leg is usually known as a deep vein thrombosis (DVT). This is when a blood clot forms in a deep leg vein which runs through the muscles of the calf and thigh.

Blood usually only clots when it is outside a blood vessel, in response to an injury to a blood vessel. This provides protection against severe blood loss. Clotting within an artery or vein can be dangerous, and can block blood flow.

While DVTs are reasonably common in older people, affecting up to one in 500 people over the age of 80, they do not usually affect people of your age. In fact, they are rare in people under the age of 40.

Possible causes

There are lots of different causes for a swollen, painful calf. It can be difficult to diagnose DVT from the symptoms alone, which is why your doctor has organised a range of tests.

Sometimes, a DVT can occur in a healthy blood vessel for no clear reason. But there are a number of factors that can increase the risk. These include:

• Being immobile. This slows down blood flow and increases the chance of a clot forming. This can happen during long surgery, and long journeys by plane or car could slightly increase the risk.
• Previous DVT/vein damage. Some conditions such as vasculitis (inflammation of the vein wall) and some medication such as chemotherapy can damage veins and increase DVT risk.
• A family history of blood clots – sometimes there are genetic causes for clots that you can inherit from your mum or dad. There are some rare genetic conditions, which cause the blood to clot abnormally, that can increase DVT risk.

Other factors that increase risk of DVT include being obese, a smoker or being over 40, especially if you have a condition that restricts mobility.

Signs and symptoms of DVT

These include swelling, pain, warm skin, tenderness and redness especially at the back of the leg, below the knee.

There are a number of tests that can be used to diagnose DVT, which will often need to be carried out in hospital. These include a specialised blood test and ultrasound scanning.

If a DVT is diagnosed, treatment usually consists of medication (called anti-coagulants) to stop the DVT from getting larger.

Once you have a firm diagnosis, your specialist will be able to advise you further.

For more help and information

Talk to your specialist doctor

Last reviewed by Great Ormond Street Hospital: 1 October 2008

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