The responsibility for allocating kidneys falls to the United Network for Organ Sharing. Basically, after an organ donor dies, medical technicians run a number of tests to see how healthy a kidney is and to determine its blood and tissue type. Next, a "procurement coordinator" inputs all of this information into a national computer network, and instantly a "match list" is generated of possible recipients. The ranking on the list is affected by a number of factors including tissue match, blood type, immune status, the length of time a candidate has been on the waiting list, and the distance between the potential recipient and the donor. Finally, the kidneys are removed and put on ice, where they can stay viable for up to 48 hours while they are being sent to a transplant center.