  Secretary of State Hillary Clinton is treated at New York
Presbyterian Hospital on Sunday. She suffered a blood clot after
a concussion earlier this month. / Emmanuel Dunand, AFP/Getty
Images  Many things can cause a blood clot in someone around the
age of Secretary of State Hillary Rodham Clinton, 65, doctors
said Sunday.  The most likely explanation for her illness is a
blood clot in the leg, brought on by her extended bed rest after
suffering a concussion earlier this month, said Cam Patterson, a
professor and chief of cardiology at the University of North
Carolina-Chapel Hill.  Patterson has no personal knowledge of
Clinton's case.  However, blood clots called deep vein
thrombosis, or DVTs, can form when people are bedridden, which
reduces blood flow to the legs, Patterson said.  "When you're
not moving around, you don't have as much circulation in your
lower extremities, and the blood sits around in your legs longer
than usual," Patterson said. "That just makes it more likely
that it's going to clot. I