now to a cnn medical investigation of liver donations. they are usually lifesavers, but sometimes they can go horribly wrong. our senior medical correspondent elizabeth cohen is joining us now with more. what have you found out, elizabeth? >> wolf, you know, we hear more about living organ donations when someone's alive they donate an organ or part of an organ and usually it's a happy ending. but sometimes things do go wrong. here's the story about two things going wrong at one hospital. >> reporter: this is a risky surgery. ryan arnold donated 60% of his liver to save his brother chad whose on liver had failed. shortly after this operation, ryan died. now cnn has learned ryan isn't the only liver donor to suffer complications at the university of colorado hospital. >> i thank god every day i'm alive because i know that could