POLYCYSTIC KIDNEY DISEASE

The kidneys are two organs, each about the size of a fist, located in the upper part of a person's abdomen, toward the back. The kidneys filter wastes from the blood to form urine. They also regulate amounts of certain vital substances in the body.

What is Polycystic Kidney Disease?

Polycystic kidney disease (PKD) is a genetic disorder characterized by the growth of numerous cysts in the kidneys. The cysts are filled with fluid. PKD cysts can slowly replace much of the mass of the kidneys, reducing kidney function and leading to kidney failure.

When PKD causes kidneys to fail--which usually happens only after many years--the patient requires dialysis or kidney transplantation. About one-half of people with the major type of PKD progress to kidney failure, i.e., end-stage renal disease (ESRD).

PKD can cause cysts in the liver and problems in other organs, such as the heart and blood vessels in the brain. These complications help doctors distinguish PKD from the usually harmless "simple" cysts that often form in the kidneys in later years of life.

Forms of PKD

In the United States, about 500,000 people have PKD, and it is the fourth leading cause of kidney failure. Medical professionals describe two major inherited forms of PKD and a noninherited form:

Autosomal Dominant PKD - The most common, inherited form. Symptoms usually develop between the ages of 30 and 40, but they can begin earlier, even in childhood. About 90 percent of all PKD cases are autosomal dominant PKD.

Autosomal Recessive PKD - a rare, inherited form. Symptoms of autosomal recessive PKD begin in the earliest months of life, even in the womb.

Acquired Cystic Kidney Disease (ACKD) - develops in association with long-term kidney problems, especially in patients who have kidney failure and who have been on dialysis for a long time. Therefore it tends to occur in later years of life. It is not an inherited form of PKD.