Kidney Transplantation

Kidney transplantation is a surgical procedure that implants a healthy kidney into a patient with renal failure. An early symptom of kidney failure is a low glomerular filtration rate. Common causes for kidney failure are diabetes, uncontrollable hypertension, and glomerulonephritis. The first kidney transplantations were done on identical twins in Boston and Paris in 1954. A major barrier to transplantation is the process of rejection in which the recipient's immune system recognizes the graft being foreign and attacks it. The antigens responsible for this reaction are the HLA system. The HLA genes are highly polymorphic and any two individuals (except identical twins) will express different HLA proteins.

Three kidney rejection reactions are hyperacute, acute, and chronic. Hyperacute rejection occurs within minutes or hours of transplantation and can be recognized by the surgeon just after the graft vasculature is anastomosed to the recipient's. This process occurs when preformed antidonor antibodies are present in the circulation of the recipient. An acute rejection occurs within days of transplantation in an untreated recipient or may occur months or years later when the immunosuppression has ended. Chronic rejection presents in patients with a sudden rise in serum creatine over a period of four to six months.

Mechanisms for increasing graft survival are to match more of the HLA genes between the recipient and the donor. Also, patients are given immunosuppressive drugs to prevent attack of the transplanted organ by the transplant recipient's immune system. Common drugs are cyclosporine, azathioprine, steroids, rapamycin, and mycophenolate mofetil. A common side effect of immunosuppressive treatment is for the recipient to be more susceptible to opportunistic infections most likely by fungal or viral organisms. Also these patients are at a higher risk for cancers that are caused by viruses. Current research to overcome this obstacle of immunosuppression is looking at inducing donor-specific tolerance in host T cells.

The United Network for Organ Sharing (UNOS) is a private, nonprofit organization that matches available organ donors with waiting transplant recipients through the national Organ Procurement and Transplantation Network (OPTN). Organ procurement is dependent on recipient time on waiting list, severity of disease, ABO blood type, and body size.

The common procedure for removal of a kidney from a living donor is a less invasive laparoscopic surgery. In the recipient, the diseased kidney is usually not removed. Instead, the donor kidney is placed inferior to the diseased kidney and the blood and urinary flows are redirected to meet the new kidney. The graft survival rate for kidneys from living donors is approximately 95 percent at one year and 76 percent at five years, whereas [Page 978]the graft survival rate for kidneys from cadaveric donors is 89 percent at one year and 61 percent at five years.