Abstract
Objective: The aim of this paper was to assess the relationships among chemical, phase and structural composition and etiopathogenic 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. Material and Methods: Twelve samples of 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. Results: Non-infectious phosphate renal calculi 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 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. Conclusion: 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.
Highlights
IntroductionNon-infectious calcium phosphate renal calculi, representing around 10% of all renal stones [1], are composed of either biological hydroxyapatite (BHAP) alone (i.e., poorly crystalline calcium-deficient hydroxylapatite containing magnesium as a minor element), or contain calcium oxalate monohydrate and/or dihydrate as a second minor constituent [2]
Non-infectious calcium phosphate renal calculi, representing around 10% of all renal stones [1], are composed of either biological hydroxyapatite (BHAP) alone, or contain calcium oxalate monohydrate and/or dihydrate as a second minor constituent [2]
The aim of this paper was to assess the relationships among chemical, phase and structural composition and etiopathogenic 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
Summary
Non-infectious calcium phosphate renal calculi, representing around 10% of all renal stones [1], are composed of either biological hydroxyapatite (BHAP) alone (i.e., poorly crystalline calcium-deficient hydroxylapatite containing magnesium as a minor element), or contain calcium oxalate monohydrate and/or dihydrate as a second minor constituent [2]. The relationship between the type of stone and the biochemical conditions under which stones form is not yet fully understood. All stones containing calcium phosphate form in urine at higher pH [3,4,5,6]. Hypercalciuria and hyperphosphaturia are often associated with phosphate stones [4,7]. Elevated urinary pH may be associated in some patients with renal tubular acidosis [8], but usually oc- OJU F.
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