Structural and microstructural characterization of human kidney stones from eastern India using IR spectroscopy, scanning electron microscopy, thermal study and X-ray Rietveld analysis

Structural and microstructural characterizations of eight human kidney stones (KS1-KS8) from eastern India have been carried out using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and thermogravimetric methods. An X-ray diffraction phase quantification revealed that three of the renal stones (KS1-KS3) were composed exclusively of calcium oxalate monohydrate (COM) and the remaining five (KS4-KS8) contained varying amounts of calcium oxalate dihydrate (40.1-53.0 wt%) and hydroxyapatite (1.3-17.3 wt%), in addition to the COM phase. The crystalline structure of COM (whewellite) at the atomic scale was redetermined through an X-ray powder diffraction study at room temperature using Rietveld analysis. Thermogravimetric analysis of KS1 reveals that COM (whewellite) is stable up to around 439 K, above which temperature anhydrous calcium oxalate is formed. The oxalate transforms to calcium carbonate at 751 K and finally to calcium oxide above 969 K. It should be emphasized that meaningful statistics in total number or gender specificity cannot be achieved with eight kidney stones.