IN a world where long haul travel, be that by road, rail, air or sea is now the norm, we find ourselves sat still for longer and longer. While only one risk factor for getting a deep venous thrombosis (DVT), the condition is among the top concerns that holiday makers attend their GP to discuss before a proposed journey.

Indeed, anyone who is envisaging travelling six hours or more is wise to consider the possibility of a DVT. Although a DVT is not life threatening, if a portion of the clot breaks off, it may travel up to the lungs, where it is referred to as a pulmonary embolus (PE).

A clot large enough to block the main blood vessel to the lungs is rapidly fatal.

Normally, blood flows in the veins from the feet upwards to the right side of the heart. If stood up, this flow is against gravity.

The calf muscles, activated by movement, squeeze these veins to help the blood back up to the heart. If for any reason this flow is interrupted, a clot may form.

The risk factors for a clot are divided into three categories. The first is sluggish blood flow, for example a period of immobility while travelling, or after an operation. Certain genetic conditions make the blood thicker, as do contraceptives and HRT containing oestrogen, smoking and obesity. The third category is direct injury to a blood vessel itself.

A DVT may have no symptoms whatsoever, and over time the clot may be broken down by the body without the person ever having been aware.

However, symptoms to look out for are a painful, swollen, red lower limb, which is larger than the opposite side.

It is unusual to get clots in both legs, but both legs may be affected if there is clot where the veins join to become one in the pelvis.

A cough, including coughing up blood, chest pain or shortness of breath may indicate a PE. Any of the above symptoms should have you seeking urgent medical advice.

Diagnosis of a DVT is based on physical examination and suspecting the condition. As the clot degrades it releases breakdown products, these give a raised reading when tested for in the blood.

An ultrasound scan of the legs will show blood flow in the limbs, with a clot showing up as a blockage. Treatment is with a blood thinner. Previously only warfarin was available, but a relatively new group of drugs called NOACs may also be used.

Although awareness of the condition is important, the actual risks of a DVT are low for those with few or none of the risk factors.

If you do undertake long journeys, simple precautions can help. Try to move about, or if on the road, have a break every few hours.

Even just moving your legs stimulates blood flow. Stick to water and avoid alcohol and caffeine as these can both dehydrate you.

Compression stockings may be beneficial, especially for those with risk factors. Taking an aspirin is not recommended, so unless you are prescribed it for another reason, it is better avoided.