Longitudinal Changes in Stone Composition and Histopathological and Proteomic Characterization of a Matrix Stone: A Case Report

Matrix stones are rare urinary calculi composed predominantly of organic matrix, with poorly understood pathogenesis. We herein report a case involving refractory matrix stones with longitudinal compositional changes and characterize the final specimen using histopathological and proteomic analyses.

A 54-year-old woman with long-standing nephrolithiasis developed bilateral ureteral obstruction and recurrent pyelonephritis, requiring multiple transurethral ureterolithotripsy procedures, ureteral stenting, and percutaneous nephrostomy. Stone composition changed sequentially from predominantly calcium oxalate to struvite to proteinaceous (consistent with matrix stones). Histopathology revealed predominantly acellular eosinophilic material, minimal mucopolysaccharide deposition, phosphotungstic acid hematoxylin-positive material suggestive of fibrin, and myeloperoxidase-positive material within the matrix. Repeated liquid chromatography-tandem mass spectrometry reproducibly identified multiple neutrophil-associated proteins.

This report documents longitudinal changes preceding matrix stone development, suggesting an association between changes in stone composition and a sustained inflammatory and infectious milieu.