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MP03-13 RANDALL'S (INTERSTITIAL) PLAQUE SHOWS DISTINCTIVE AUTOFLUORESCENCE IN HUMAN KIDNEY STONES COLLECTED DURING ENDOSCOPIC PROCEDURES

INTRODUCTION AND OBJECTIVES: The early growth of kidney stones is still little understood, but it appears that a significant proportion of calcium oxalate (CaOx) stones begin as overgrowths onto interstitial (Randall's) plaque (RP). RP occurs initially as a deposition of the calcium phosphate mineral, apatite, in the connective tissue surrounding tubules and vessels in renal papilla. By some process the apatite of RP becomes exposed to calyceal urine and growth of a CaOx stone begins. The aim of this study was to learn more about the mineral and protein changes at the interface between RP and the stone. METHODS: Small stones found attached to the renal papilla were removed during percutaneous or ureteroscopic procedures. Stones were scanned using micro CT (at voxel sizes of 3 &mgr;m or less), mounted onto polystyrene, and ground down using fine emery paper to expose the stone interior. Repeated micro CT was used to verify location of exposed plane within each stone. Exposed interior of stones was then imaged using fluorescence (with excitation at 405, 488, 552, and 643 nm) and infrared spectroscopic (FT-IR) microscopic methods. RESULTS: In 9 stones from 6 patients the region of stone overgrowth onto RP was exposed. In all cases FT-IR showed micro CT-confirmed RP to contain only apatite, and overgrowth mineral to be CaOx (sometimes with veins of apatite). Stones were highly autofluorescent with widely varying patterns in the CaOx overgrowth regions, but autofluorescence in RP was consistently and almost exclusively in the blue range only. The blue autofluorescence of RP was confirmed in sections from papillary biopsy. CONCLUSIONS: This method of stone preparation allows the study of mineral and protein changes at the interface between RP and urinary mineral in nascent CaOx stones. The unique autofluorescence character of RP should allow for easier identification of this important tissue calcification. Figure. No caption available. Source of Funding: NIH P01 DK056788