Polycystic disease may be caused by a defect in the renal tubular system that deforms nephrons and results in cyst like dilations along their course. It is the most common inherited disorder of the kidneys. The kidney tissue is riddled with fluid-filled cysts and small holes, ranging in size from a pinhead to the diameter of an egg.
These cysts gradually increase until they squeeze out the normal tissue, interfering with kidney function and causing uremia.
The chief symptom is weight gain. The kidneys themselves may enlarge from their normal 0.25kg(0.5lb) to as much as 14kg (30lb).
Although the disease is progressive and ultimately fatal, its advance can be slowed by diet, drugs and regulation of fluid intake.