Calcium oxalate precipitation in model systems mimicking the conditions of hyperoxaluria

This work focuses on systematic research of spontaneous precipitation of calcium oxalate in model systems mimicking the chemical conditions typical for hyperoxaluria. For this purpose, model systems of three different complexities (simple, NaCl and artificial urine system) and two initial pH (pHi = 5.0 and pHi = 9.0) at 37 ºC are studied. In all investigated systems, dominant precipitation of calcium oxalate monohydrate (COM) is observed, except in artificial urine system at pHi = 9.0, ci(C2O42-) ≥ 6.0 mmol dm-3 and ci(Ca2+) ≥ 7.5 mmol dm-3 where precipitation of a mixture of calcium oxalate monohydrate and calcium oxalate dihydrate (COD) occurrs. The significant difference is mainly observed in COM crystal morphology. In a simple system, COM precipitates in a dendritic form, in NaCl system dendritic form and irregular shapes are found, while in the artificial urine, prismatic hexagonal and aggregated COM crystals precipitate.