Deep vein thrombosis

It never occurred to Lynn E. Stewart that the swollen knee she got while hiking could kill her.

It very nearly did.

Deseret Morning News graphic Deep vein thrombosis Requires Adobe Acrobat.

Her doctor said she'd strained it and to stay off it for about three days. So she did.

When her exile into idleness ended, Stewart bustled around, getting ready for work the next day, shopping, cleaning up.

That night, as she was talking to a friend on the phone, she was slammed by a pain unlike anything she'd ever felt. "I felt like someone had just shoved a knife in my back, toward my right side. I literally started gasping for air."

At the hospital, it didn't take long to diagnose her problem: a pulmonary embolism, caused by deep vein thrombosis. While she was taking it easy and staying off her feet, blood was pooling in her leg. And when she abruptly resumed activity, part of the clot broke off and lodged in her lung. In all, doctors had to dissolve three blood clots.

Stewart was in the hospital for more than a week. And she was lucky. She survived. But she says she's never experienced that kind of pain before, and she hopes never to again. "The pain was unbearable for several days, even with morphine."

A lot of Americans first learned about deep vein thrombosis and pulmonary embolism in April 2003, when popular and respected NBC reporter David Bloom, embedded with troops in Iraq, died — apparently as a result of a pulmonary embolism. It was believed that he developed the clot from lying prone inside a tank, not moving his legs, for long periods of time.

Next came warnings about airline travel and the importance of flexing your leg muscles when flying, if moving around isn't possible. And of the dangers associated with complete bed rest.

Deep vein thrombosis is a potential disaster born of inactivity.

A deep vein thrombosis is a blood clot, usually in the legs, though it can occur in the arms. It's located, just as the name says, in the deep veins that run through muscle tissues, rather than superficial veins such as those associated with varicose veins, said Dr. Colleen Harker, interventional radiologist at LDS Hospital.

Deep veins carry blood back to the heart. A deep vein thrombosis either partially or completely blocks blood flow in the vein, resulting in swelling and possible discomfort. Sometimes there's localized pain or tenderness, and the area is warm to the touch. The skin may discolor. And sometimes, there's no symptom at all.

If a piece breaks off and travels to the lung, it's a pulmonary embolism, dangerous because it blocks the pulmonary artery or one of its branches, in turn stopping blood flow to the heart.