Microstructural Studies and Elemental Imaging of Renal Stones by Scanning Electron Microscopy–Energy-Dispersive X-ray Spectroscopy

Globally prevalent renal stone diseases are extremely painful and affect people all over the world. Given the importance of the role of elements in their formation and the fact that the growth and genesis of renal stones are imprinted in their morphology, the etiology of lithiasis could be studied with relevant analytical tools. The prime objective of this investigation is to describe the compositional structure and morphology of nineteen surgically removed renal stones. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy is used to obtain the chemical and structural compositions of the stones. Thermal gravimetric and differential scanning calorimetry analyses were also performed to understand their thermal behaviors. Calcium oxalate monohydrate, along with some traces of calcium phosphate, uric acid, and sodium urate, represents the main mineralogical phase of the renal stones used in the present study. A scanning electron microscopic study showed that calcium oxalate monohydrate crystals had a sphere-like, clumping-like morphology with irregularities in their sizes and orientations and were more tightly packed and regularly ordered in comparison to the uric acid crystals. Elemental imaging and mapping of the main and trace elements within the renal stones were also obtained, which reveals the heterogeneous nature of stones.