Polycystic Kidney Disease

Q. What is polycystic kidney disease?

A. 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. The kidneys filter wastes from the blood to form urine. They also regulate amounts of certain vital substances in the body.

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.

Q. What are the different types of polycystic kidney disease (PKD)?

A. There are three different types of PKD, which vary according to the way people can get the different forms. One of the inherited forms is domininant, meaning that those who have the gene from either their mother or father, will have the disease. The other inherited form, which is recessive, only develops in those individuals who have copies of the gene from both parents; otherwise, they carry the gene and may pass it to their children, but they themselves may not have kidney disease.

Autosomal dominant PKD is 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 is 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.