High resolution radiography of cadaveric kidneys: Unraveling the mystery of Randall's plaque formation

Purpose: We used high resolution radiography to identify and characterize Randall's plaques in cadaveric kidneys. Materials and Methods: A total of 50 consecutive sets of cadaveric kidneys was fixed, bivalved and imaged with micro-focal spot magnification radiography. Papillary calcifications were identified, localized and processed for light microscopy. Special immunohistochemical stains were implemented to aid localization of ectopic calcifications. Patient medical records and autopsy results were retrospectively evaluated and correlated with radiographic papillary calcifications. Results: Of the 92 renal units with complete data 52 (57%) had radiographic evidence of renal medullary calcifications consistent with Randall's plaques. Unlike the original description of this condition, calcifications extended deep into the papilla. A history of hypertension was the only clinical parameter correlating with papillary calcifications. Calcium deposition was localized to the basement membrane of collecting tubules and vasa recta, and papillary interstitium. Conclusions: Randall's plaques are not merely subepithelial deposits. Rather, they appear to extend deep within the papilla, and are intimately associated with collecting tubules and vasa recta. An association between papillary calcifications and urinary stone formation has yet to be proved but is under investigation.