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What is deep vein thrombosis?

'Economy class syndrome' uncovered

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What is deep vein thrombosis?

Asked by David White of Ramsgate, South Africa

Deep vein thrombosis (aka deep venous thrombosis) or DVT is the formation of a blood clot (thrombus) in a deep vein of the body. It most commonly affects the leg veins but can affect the arm or pelvis veins.

DVT has become popularly known as "economy class syndrome" because of its association with the immobility and dehydration that can occur in long distance air travel.

On average, DVT occurs in about one in every 1,000 people per year. However, "[N]early one million patients are treated for deep venous thrombosis annually in the United States" according to vascular surgeons Drs K Kasirajan, R Milner, and E Chaikof of Emory University in Atlanta, writing in the June 2006 Seminars in Vascular Surgery.

Although there may frequently be no symptoms of DVT, usually symptoms that do appear include pain, swelling, redness of the leg (or arm or pelvis), and dilatation of the surface veins.

DVT can be very serious. Between one and five per cent of those with DVT die. They die not from DVT itself but from a pulmonary embolism - the most dangerous complication of DVT.

In a DVT pulmonary embolism, the blood clot in the leg (or arm or pelvis) becomes dislodged from its site and blocks (embolises) the arterial blood supply of one of the lungs. Risk factors of DVT include age, immobilisation, tobacco use, female gender, use of oral contraceptives, as well as Virchow’s triad - the three factors that affect blood clot formation (rate of blood flow, thickness of blood, and quality of the blood vessel wall).

DVT occurs far more often in older people. It occurs in only about one in 100,000 of those under age 18. This is because children are relatively more active, have better quality veins, and even have a higher rate of heartbeats per minute. As the population ages, more DVT would be expected to be seen, and is.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

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