Kidney Function and Urologica... Health Article

Kidney failure

Kidney failure—when the kidneys are no longer able to adequately eliminate waste materials from the blood—does not generally happen until the kidneys lose 70% or more of their function, since they normally have considerably more capacity than is needed. In acute kidney (or renal) failure, the kidneys stop functioning suddenly. It usually has a cause other than kidney disease, such as blood loss, dehydration, a drug reaction, or a variety of other serious conditions. Symptoms include decrease in urination, swelling, drowsiness, and irregular heartbeat. Chronic kidney failure, which can be caused by a variety of kidney disorders, occurs gradually. Many types of kidney disease have few symptoms in their early stages, allowing significant deterioration to take place before kidney failure becomes apparent. Often, fatigue is the first symptom of chronic kidney failure, followed by loss of appetite, low urine output, and thirst. Other symptoms include pallor, headaches, nausea, cramps, facial puffiness, and dry or itchy skin. Kidney failure also slows growth and can even stop it altogether. The first measures in treating kidney failure include dietary changes, oral nutritional supplements, and medications that lower the levels of phosphate absorbed into the blood from the intestine. Blood pressure must also be controlled. In most cases, the condition progresses to end-stage renal disease (deterioration to 5-10% of normal capacity), and dialysis or transplantation often becomes necessary.

There are several types of dialysis. Hemodialysis is a means of filtering the blood through a machine—often called an artificial kidney—that performs the functions of a normally working kidney. Blood is pumped from the body into an artificial membrane that performs a filtering operation similar to that of the kidney's own glomeruli while a special dialysis solution, called dialysate, helps regulate the blood's chemical content and remove waste and excess fluids. The patient, who often has a shunt surgically implanted in an arm or leg artery to simplify the connection process, undergoes dialysis sessions two or three times a week in the hospital, at a special dialysis center, or at home with proper medical supervision. Each session lasts about four hours.

Instead of using an external machine, peritoneal dialysis uses the small blood vessels in the membranes of the patient's own peritoneal cavity as a filtering agent for the blood. A catheter is inserted into the abdomen, and a fluid similar to that used for hemolytic dialysis is infused through it, providing the body with needed electrolytes and carrying waste materials with it when it drains. Peritoneal dialysis may be administered several different ways. The intermittent form, which is repeated every hour for 24 to 48 hours, is generally used for acute renal failure that is not expected to require long-term treatment. Continuous ambulatory peritoneal dialysis (CAPD) is performed four or five times a day, and the dialysis fluid is left inside the patient between sessions, for periods of four to six hours. Continuous cycling peritoneal dialysis is performed at night while the child sleeps. During this period, the peritoneal cavity is filled and flushed several times.

A child with end-stage renal failure is also a candidate for a kidney transplant, one of the most successful and frequently performed transplant operations. Although the body has a natural tendency to reject all foreign matter, it is less likely to reject the transplanted kidney if the tissue of the donor closely matches that of the recipient. The most compatible donor organs are those from siblings and parents, in that order. If a kidney from a relative isn't available, transplant centers throughout the country are contacted for a compatible kidney from an accident victim or other recently deceased donor. The operation, which is not a complicated one, takes about four hours, followed by up to six weeks in the hospital. The medication cyclosporine, which suppresses the body's immune system, is commonly taken by transplant recipients, with the dose lowered sharply after the first year following surgery, since an immune system suppressant also impairs the body's ability to fight infections.

The first two years are the most crucial period for acceptance or rejection of the new kidney. A kidney donated by a sibling has a two-year success rate of 90-95%; a kidney transplant from a nonrelative has a success rate between 65 and 80%.

Books

De Wardener, H.E. The Kidney: An Outline of Normal and Abnormal Function. New York: Churchill Livingstone, 1985.

National Institutes of Health. What You Need to Know about Wilms' Tumor. National Institutes of Health, Public Health Service, U.S. Dept. of Health and Human Services, 1983.

Schrier, Robert W. Diseases of the Kidney. 4th ed. Boston: Little, Brown, 1988.