KIDNEY TRANSPLANT

also called Renal Transplant, replacement of a diseased or damaged kidney with a healthy one obtained either from a living relative or a recently deceased person. Although kidney transplants were carried out in the late 1950s, clinically significant transplantation did not begin until around 1963, when the immunosuppressive drug azathioprine was developed to help counteract the rejection of the new organ by the body's immune system. Because a kidney from a related donor is less likely to be rejected by the body, transplants from living relatives are more successful than those from cadavers. Nevertheless, cadavers are today the most common source for transplants because of their greater availability and because they obviate the risk to living donors. Before transplantation, the immunologic characteristics of the recipient are carefully analyzed and a donor selected whose immunologic profile is matched as closely to the recipient's as possible. Traits used in determining a successful match include blood groups and tissue markers that enable the immune system to distinguish between the body's own tissues and foreign tissue. If the kidney is to come from a live donor, the recipient may undergo dialysis for several weeks before surgery to control existing kidney disease. Because kidneys from cadaver donors survive only a short time after removal, dialysis treatment for the recipient is not always possible. The operation will be cancelled if the recipient has any infection, because of the risk that infection will spread, protected by immunosuppressive medication. The new kidney is implanted in the iliac fossa, a space in the small of the back; usually a right kidney is placed in the left fossa and vice versa to aid in making new attachments between blood vessels. The renal artery and vein are connected to the iliac artery and vein, and the ureter from the new kidney is either connected to the existing ureter or attached directly to the bladder. Formerly both of the recipient's kidneys were removed; they are now left in place unless they are infected or are too large to permit the new organ to be implanted. The rejection rate remains high, especially for cadaver kidneys, and some patients receive two or three kidneys before the body accepts one. Rejection may begin within minutes after the new organ is attached. Acute rejection, in which the tissues of the new kidney are injured by the immune system and the organ suddenly fails to function, can occur up to several years after operation but is most common in the first three months. Chronic rejection, in which deterioration of kidney function is more gradual, also may occur. Large doses of immunosuppressive drugs, along with drugs that retard the formation of blood clots, can halt acute rejection and save the transplant; if the medication does not help, the kidney is usually removed before infection or other complications set in. Kidneys taken from living donors often begin to function immediately, while those from cadavers may take up to two weeks for tissues to adjust and become functional. If there are no complications from the transplant and no signs of rejection, the recipient can resume a virtually normal life within two months, although he must usually continue taking immunosuppressive drugs for several years. Because these drugs lower resistance to infection, however, other systemic complications may arise with time.