Electron probe micro-analysis reveals the complexity of mineral deposition mechanisms in urinary stones

Urinary stones are complex mineralogical formations in the urinary system often impairing the kidney function. Several studies have attempted to understand the mechanisms of stone formation and growth; however, it remains to be fully explored. Here, we present a detailed investigation on the morphological and mineralogical characterizations of urinary stones. Structural properties of different types of urinary stones were done by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field-emission scanning electron microscope (FE-SEM) analyses. X-ray maps of major and the trace elements were obtained using electron microprobe (EPMA) technique. Basic metabolic panel and urinary parameters of the patients were used for comparing mineral compositions among stone types. The study included five major types of stones identified based on the FTIR spectra. FTIR and XRD helped in identifying the major components of these stones. FE-SEM images revealed distinct microstructure and morphology of the stones among the stone types. EPMA analysis showed the presence of many metals other than calcium and certain non-metals within the urinary stone matrix at measurable levels, sometimes with distinct distribution patterns. The study demonstrates the characteristic micro-structure, morphology, distribution, and composition of elements in different stone types. Findings of the study provide scope for understanding the complex mechanisms involved in the urolithogenesis and association of trace elements in it.