Presented by: James C. Williams, Jr. PhD
Indiana University School of Medicine

Introduction

Recent work has shown that mechanisms of stone growth can be demonstrated at the microscopic level using fluorescence microscopy. The objective here was to study multiple stones to observe patterns of mineral and organic deposition within and between patients.

Materials

Stones were removed by basket during endoscopic procedure, and a total of 12 stones were studied from 3 patients. All stones were verified by micro CT as having grown on Randall’s plaque by residue visible on the stone. Each stone was mounted on polystyrene and ground down to reveal a planar surface inside the stone. The stone was then imaged using confocal microscopy (Leica SP8) with a water immersion lens (20x, 0.75 NA). Each stone was ground repeatedly to collect as many interior planes as possible, with micro CT verification of each plane of section and mineral regions exposed.

Results

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Within a patient, similarities of layering (both thickness and color) were apparent in stones from the same kidney. Deposition of calcium oxalate monohydrate showed variable patterns of fluorescence even in adjacent layers. Several stones showed evidence of episodic growth by deposition of aggregates of dihydrate crystals, and dihydrate crystals showed only scattered regions of fluorescence in the blue region. Regions of apatite adjacent to Randall’s plaque showed yellow fluorescence distinctly different from apatite deposited in later stone overgrowth. Randall's plaque showed fluorescence in the deep blue range as previously reported.

Conclusion

The unique fluorescence of apatite laid down as the first overgrowth on Randall’s plaque is suggestive of special urine molecules deposited at the initiation of stone growth. Outside of this consistent finding, fluorescent molecules laid down with mineral in calcium oxalate stones are not universal among patients, but stones from the same kidney showed similar fluorescence patterns.

Funding

NIH P01DK056788; NIH R01DK124776

Co-Authors

James E. Lingeman, MD
Indiana University School of Medicine