Metaplastic cartilage in nondysplastic kidneys.

Four hundred ninety-seven patients representing the 525 total or polar nephrectomies performed at the Children's Memorial Hospital from 1938 to 1973 (excluding 1947), were reviewed retrospectively to determine the incidence and characteristics of renal dysplasia. The 46 specimens with this histologic diagnosis all exhibited typical primitive ducts with 13 being also associated with cartilage formation. In five patients, kidney showed focal chondrous metaplasis of the interstitium in association with chronic inflammation but without primitive ducts. The findings strongly suggest that the renal interstitium occasionally may react to injury by chondrous metaplasia and that, in the absence of primitive, ducts, cartilage in the kidney is not pathognomonic of renal dysplasia.