Secretary of State Clinton Released from Hospital

And, we have big new tonight on secretary of state hillary clinton. She has been discharged from the hospital, just this evening. After four days under treatment for a blood clot near her brain. And... See More

And, we have big new tonight on secretary of state hillary clinton. She has been discharged from the hospital, just this evening. After four days under treatment for a blood clot near her brain. And abc's chief medical editor dr. Richard besser tells us what we know about her condition tonight. Reporter: Just hours ago, secretary clinton was seen outside of the hospital, reportedly for testing. Look again. Here she is, up and walking to her car. The state department today told us she's begun quite active on the phone with calls to her staff. The 65-year-old secretary of state is the most traveled in history. 112 countries, almost a million miles logged, more than a year of her life shuttling from nation to nation. But this clot has grounded her. The tricky treatment? Anticoagulants, also called blood thinners. Doctors need to monitor a delicate balance of dosage. They're trying to thin the blood around the clot to stabilize it and prevent it from getting bigger, while her body works to try to shrink it. Her doctors haven't said what caused the clot. But possible factors putting clinton at risk? Dehydration from the stomach flu that she had in december. Or is it somehow related to the concussion sustained at the same time? Or could she have a clotting disorder, which makes her blood more susceptible to clot formation? Secretary clinton had a blood clot in 1998 in her leg. We learned tonight the good news that secretary clinton has been discharged from the hospital. And according to the state department, her medical team told her she's making good progress and she should expect a full recovery. Thank you so much, rich.