Beware of leg clots, acting US surgeon general has warned. Dangerous blood clots may affect up to 600,000 Americans a year.
Dr. Steven Galson launched a campaign Monday to get patients and doctors to recognize the potential emergency.
Deep-vein thrombosis or DVT is caused by sitting rigidly for too long, which can cause a blood clot to form in a deep vein, usually in the calf, thigh or groin. If the clot breaks loose and journeys to the lungs, it may lead to pulmonary embolism blocking an artery in the lungs and reducing oxygen supply.
"It's a silent killer. It's hard to diagnose," Dr.Galson said. "I don't think most people understand that this is a serious medical problem or what can be done to prevent it."
The World Health Organization has said that passengers travelling for four hours or more face double the risk of developing the clots. The agency recommends that travellers get up for a short walk and exercise their calves by moving their feet and ankles hourly.
In Monday's report, the surgeon general and the Agency for Healthcare Research and Quality said travellers aren't the only ones at risk. The report's authors estimated between 350,000 and 600,000 Americans have the clots each year, and at least 100,000 deaths may be directly or indirectly related to the clots.
People are at high risk for the clots if they:
Have had surgery recently.
Are over age 65.
Take birth control pills or hormone replacement therapy.
Have cancer, a bad bruise or a broken bone.
Have been immobile during long trips.
Smoking and obesity also increase the risk.
People who show no symptoms but have a relative who has suffered a blood clot should tell their doctor about the family history.
Pain, especially in the calf.
A warm spot or red, discoloured skin on the leg.
Shortness of breath.
Pain when breathing deeply.
The education campaign also applies to doctors, since studies suggest that one-third of patients who need blood thinners before surgery don't get them, Galson said.
The report includes cases of patients who are turned away despite symptoms, such as Le Keisha Ruffin, whose leg and groin pain were repeatedly chalked up to a healing caesarean-section scar.
When her leg swelled to triple or quadruple its normal size and she passed out, that was the tip-off for doctors. After a month in hospital, Ruffin, now 32, needed extensive physical therapy to resume walking normally.
Clots "tend to fall through the cracks" because they cross so many areas of medicine, said Dr. Samuel Goldhaber, chairman of the Venous Disease Coalition and a cardiologist at Boston's Brigham & Women's Hospital.
The surgeon general's workshop on DVT in 2006 revealed a lack of consensus in how health professionals deal with the disease or the best approaches, agreed Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute, in a preface to the report.
The report therefore emphasizes the need for increased awareness of DVT and pulmonary embolism, evidence-based guidelines, and more research on its causes, prevention and treatment, CBC News reports with AP.