A classification of renal cysts.

Renal cysts are a heterogeneous group comprising heritable, developmental, and acquired disorders. The classification presented here has been developed, as have several others in the past, to incorporate radiographic, functional, and genetic contributions in its clinicopathologic correlations. Its major categories are as follows: (1) dysplastic cysts arising in kidneys that have undergone abnormal morphogenesis and differentiation; (2) polycystic disease of autosomal recessive and autosomal dominant types; (3) heritable syndromes of multiple malformations with renal cysts resulting from presumed metabolic injury; (4) isolated cortical cysts of unknown pathogenesis; (5) medullary cysts of several types, including medullary sponge kidney and the progressive syndromes of medullary cystic disease, familial juvenile nephronophthisis, and renal-retinal dysplasia; (6) acquired parenchymal cysts of diverse origins; and (7) extraparenchymal cysts. This classification, which has been revised repeatedly over the years, is still tentative and undoubtedly will be revised again.