Structure and Composition of Non-Infectious Phosphate Calculi Formed in Patients with Low and High Urinary Phosphate Concentrations

Abstract

<p> <b><span>Objective:</span></b><span> The aim of this paper was to assess the relationships among chemical, phase and structural composition and <a name="OLE_LINK7"></a><a name="OLE_LINK3"></a><span>etiopathogenic</span> factors of non-infectious phosphate calculi formed in patients with low and high urinary phosphate concentrations, and to characterize the mechanism of their formation related on biochemical results. <b>Material and Methods:</b> Twelve samples of<b> </b>phosphate renal calculi were obtained, 4 from patients with low phosphaturia and 6 from patients with high urinary phosphate concentrations. Their chemical composition was determined qualitatively by energy dispersive X-ray analysis and quantitatively by spectrophotometric and thermal analysis; and their phase composition was determined by Fourier transform infrared transmission spectroscopy and X-ray diffraction. The structure of the calculi was assessed by scanning electron microscopy. <b>Results:</b> Non-infectious phosphate renal calculi </span><span>of patients with low phosphaturia consist of poorly crystalline carbonate hydroxyapatite, whereas those of patients with high urinary phosphate concentrations consist of poorly crystalline hydroxyapatite with </span><span>some amount of calcium oxalate crystals. Calculi of patients with high urinary phosphate concentrations are formed at urinary supersaturation with respect to hydroxyapatite and calcium oxalate about 4 times higher than in patients with low phosphaturia. <b>Conclusion:</b> In patients with low phosphaturia, the non-infectious phosphate renal calculi are formed in urine near pH 7 and contain only poorly crystalline carbonate hydroxyapatite. In patients with high urinary phosphate concentrations and hypercalciuria, the calculi are formed in urine near pH 6 and consist of both poorly crystalline hydroxyapatite and some amount of calcium oxalate crystals.</span><span></span> </p