engleski

Calcium oxalate precipitation in model systems mimicking hyperoxaluria conditions

According to the latest epidemiological studies, the prevalence of urolithiasis has been increasing for the past few decades, especially in industrialised countries, possibly due to improved standard of living and modern dietary habits. Urolithiasis is the formation of crystals in the urinary tract and is a specific form of pathological biomineralisation. It is a result of physiochemical mechanisms and involves the processes of nucleation, crystal growth and aggregation. Many factors may contribute to crystallisation and urinary stone formation including pH, ionic strength and the presence or absence of substances that can promote or inhibit the process [1]. Different metabolic disorders, which can be inherited or developed, are considered to be important risk factors and include hyperoxaluria, hypercalciuria, hypocitraturia and changes in acidity of the urine. Hyperoxaluria is associated with oxalate urinary tract stones and oxalate crystal deposition in tissue [2]. In this work, systematic research of spontaneous calcium oxalate precipitation in three systems with different levels of complexity (simple, NaCl and artificial urine system) and two different initial pHs (pHi = 5.0 and 9.0) was conducted. In all investigated systems which simulate the conditions of hyperoxaluria, a dominant precipitation of calcium oxalate monohydrate (COM) was noted, except in the artificial urine system at pHi = 9.0, where precipitation of a mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) occurred. The most pronounced difference was observed in COM morphology. In the simple system crystals precipitated in dendritic form, in the NaCl system they took a dendritic form with more or less irregular shaped crystals, while in artificial urine aggregated and prismatic hexagonal COM crystals precipitated.

calcium oxalate monohydrate ; hyperoxaluria ; kidney stones

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