Organ transplant is a complicated procedure that necessitates a close match between the recipient and donor. Both the donor and the recipient must have compatible blood types. Other factors, depending on the organ involved, may be relevant. For example, kidney donors and recipients must have compatible antibodies and body sizes. The transplant waiting list is managed by the Procurement of Organ Transplant Network. When a person reaches the top of the waiting list, they will be given a transplant as soon as a suitable donor becomes available. When an organ becomes available, the person in need of a transplant must respond quickly to their doctor's call. The organ recipient will need to stay in the hospital for a few days after the transplant while doctors monitor their condition. When organ recipients become ill, they can become critically ill. Their body may even reject the new organ, so any signs of infection, such as a fever, should be reported to a doctor.