Which hereditary disorder of the kidneys is characterized by cysts replacing normal kidney tissue?

Polycystic Kidney Disease (PKD) is the hereditary disorder of the kidneys characterized by the formation of numerous cysts that replace normal kidney tissue. This condition leads to the kidneys becoming enlarged and can impair their ability to function properly over time. PKD is a genetic disorder and can be inherited in either an autosomal dominant or autosomal recessive manner, depending on the specific type of PKD.

Other options differ in their definitions and characteristics. Nephrolithiasis refers to the presence of kidney stones, which does not involve the formation of cysts. Cystitis is an inflammation of the bladder, often due to infection, and is not related to cyst formation in the kidneys. Enuresis, commonly known as bedwetting, does not pertain to kidney structure but instead to a urinary control issue. Thus, the defining characteristic of cysts replacing kidney tissue makes Polycystic Kidney Disease the correct answer.