Definition of Polycystic kidney disease:

Polycystic kidney disease is a kidney disorder passed down through families in which multiple cysts form on the kidneys, causing them to become enlarged.

Causes, incidence, and risk factors:

Polycystic kidney disease (PKD) is passed down through families (inherited), usually as an autosomal dominant trait. If one parent carries the gene, the children have a 50% chance of developing the disorder.

Autosomal dominant PKD occurs in both children and adults, but it is much more common in adults, with symptoms often not showing up until middle age. It affects nearly 1 in 1,000 Americans. The actual number may be more, as some people do not have symptoms. The disorder may not be discovered unless tests revealing the disease are performed for other reasons.

An autosomal recessive form of polycystic kidney disease also exists and appears in infancy or childhood. This type tends to be very serious and progresses rapidly, resulting in end-stage kidney failure and generally causing death in infancy or childhood.

Persons with PKD have multiple clusters of cysts form on the kidneys. The exact action that triggers cyst formation is unknown. In early stages of the disease, the cysts cause the kidney to swell, disrupting kidney function and leading to chronic high blood pressure and kidney infections. The cysts may cause the kidneys to increase production of erythropoietin, a hormone that stimulates production of red blood cells. This leads to too many red blood cells, rather than the anemia seen in chronic kidney disease.

Bleeding in a cyst can cause flank pain. Kidney stones are more common in people with PKD.

PKD is associated with the following conditions:

• Brain aneurysms
• Cysts in the liver, pancreas, and testes
• Diverticula of the colon

As many as half of people with PKD have cysts on the liver. A personal or family history of PKD increases your risk for the condition.