Last updated: 11/24/2009

Patients with chronic renal disease who need a transplant and do not have a living donor registered with United Network for Organ Sharing (UNOS) to be placed on a waiting list for a cadaver kidney transplant. UNOS is a non-profit organization that...

is under contract with the federal government to administer the Organ Procurement and Transplant Network (OPTN) and the national Scientific Registry of Transplant Recipients (SRTR).

Kidney allocation is based on a mathematical formula that awards points for factors that can affect a successful transplant, such as time spent on the transplant list, the patient's health status, and age. The most important part of the equation is that the kidney be compatible with the patient's body. A human kidney has a set of six antigens, substances that stimulate the production of antibodies. (Antibodies then attach to cells they recognize as foreign and attack them.) Donors are tissue matched for 0–6 of the antigens, and compatibility is determined by the number and strength of those matched pairs. Blood type matching is also important. Patients with a living donor who is a close relative have the best chance of a close match.

Before being placed on the transplant list, potential kidney recipients must undergo a comprehensive physical evaluation. In addition to the compatibility testing, radiological tests, urine tests, and a psychological evaluation will be performed. A panel of reactive antibody (PRA) is performed by mixing the patient's serum (white blood cells) with serum from a panel of 60 randomly selected donors. The patient's PRA sensitivity is determined by how many of these random samples his or her serum reacts with; for example, a reaction to the antibodies of six of the samples would mean a PRA of 10%. High reactivity (also called sensitization) means that the recipient would likely reject a transplant from the donor. The more reactions, the higher the PRA and the lower the chances of an overall match from the general population. Patients with a high PRA face a much longer waiting period for a suitable kidney match.

Potential living kidney donors also undergo a complete medical history and physical examination to evaluate their suitability for donation. Extensive blood tests are performed on both donor and recipient. The blood samples are used to tissue type for antigen matches, and confirm that blood types are compatible. A PRA is performed to ensure that the recipient antibodies will not have a negative reaction to the donor antigens. If a reaction does occur, there are some treatment protocols that can be attempted to reduce reactivity, including immunosuppresant drugs and plasmapheresis (a blood filtration therapy).

The donor's kidney function will be evaluated with a urine test as well. In some cases, a special dye that shows up on x rays is injected into an artery, and x rays are taken to show the blood supply of the donor kidney (a procedure called an arteriogram).

Once compatibility is confirmed and the physical preparations for kidney transplantation are complete, both donor and recipient may undergo a psychological or psychiatric evaluation to ensure that they are emotionally prepared for the transplant procedure and aftercare regimen.