Knoxville (WVLT) The discovery of a blood clot in Vice President Dick Cheney's left leg Monday have many people questioning how serious the problem is.
It's also called deep vein thrombosis and the condition can be fatal if left untreated.
Medical Reporter Jessa Goddard has more on how these blood clots form, and how they're treated.
NBC News Correspondent David Bloom died in 2003 of a blood clot after spending days in a cramped military vehicle while covering the invasion of Iraq.
Treated properly, it poses a small threat.
Untreated and unrecognized, it's a very serious problem.
A blood clot can be both very treatable, and fatal.
It can present symptoms, and be undetectable.
Vice President Cheney visited his doctor's office in Washington after feeling minor discomfort in his calf.
Dr. David England, with the Farragut Family Practice says, "very often, it can be asymptomatic, and thus you have to have a degree of suspicion for it."
Dr. England says many people suffer deep vein thrombosis after spending long periods without moving, such as passengers on long airline flights.
To prevent DVT, airlines often encourage passengers to walk the aisles and wiggle their feet.
"It's actually very common. There are approximately 250,000 hospitalizations in this country every year with it. And approximately 50,000 deaths."
Cheney spent about 65 hours on a plane on a nine day, round the world trip that ended last week.
But flying is not the only risk.
It extends to anyone older than 60, or who has heart failure.
And Cheney's health has long been an issue.
He's had four heart attacks, quadruple bypass surgery, two artery clearing angioplasties and an operation to implant a pacemaker in his chest.
Cheney will be treated with blood-thinning medication over several months.
Dr. England says, "sometimes, it doesn't require treatment with medication, sometimes it does. If the clotting is below the knee, it's less likely to cause serious problems and can be treated as an outpatient."
Doctors often initially treat DVT patients with an anticoagulant medicine called Heparin, which can sometimes now be injected in shot form.
DVT patients are then given the blood-thinning drug Warfarin, which sometimes must be taken for months.
Blood clots that form deep in the legs can become fatal, if they break off and float into the lungs.
And that's called a pulmonary embolism, killing about 60,000 Americans each year.