UPDATED 0:46 AM EST, December 31, 2012
Blood clots like the one that Secretary of State Hillary Rodham Clinton is being treated for following her recent concussion can occur for a host of reasons. How serious a clot is depends on where it is and why it formed, doctors say. A Clinton aide would not say where hers is located.
WHAT THEY ARE: Blood pools and thickens into a clot after an injury or because of a heart problem, clogged arteries or other condition. Clots also can break off and travel to another part of the body.
