engleski

EVALUATION OF METHODS FOR URINE INHIBITORY POTENTIAL FOR PRECIPITATION OF CALCIUM OXALATE

Renal lithiasis is a significant medical and social problem with still a high recurrence rate (3%-5%) worldwide. In Croatia urinary and/or renal stones are composed predominantly of calcium oxalate and phosphate stones (about 75%), uric acid (about 10% - 12%) and sometimes so-called infection stones struvite (about 10% - 15%). Major factors contributing to renal stone formation are urine supersaturation and various metabolic factors. However urine can contain various substances which by different mechanisms can inhibit the precipitation process. The objective of this paper is to evaluate and compare several chemical methods for distinguishing between stone formers and non-stone formers. The examined methods are based on testing the inhibitory capacity of urine with respect to precipitation of calcium salts. The two methods in question are: a) initiation of precipitation from whole urine by addition of calcium oxalate monohydrate seed crystals – this method monitors ionic calcium concentration with seed crystals of calcium oxalate monohydrate (COM) (initiated precipitation) and without (spontaneous precipitation) after 3h and 24h incubation at 37˚C. Results are shown according to the following criteria: Δc (Ca) = c (Ca) spont.prec. – c (Ca) init.prec. b) testing the capacity of urine for calcium complexing by adding calcium solution to whole urine – urine samples (first morning urine) are titrated with calcium chloride solution (c(CaCl2)= 0.1 moldm-3). The discriminating criteria for the results is the slope of the titration curve. Preliminary research shows that these two methods have a great potential for discriminating between the stone formers and non-stone formers. The theoretical background experimental design and parameters for discrimination between urines of stone formers and non-stone formers are explained for both methods. The results for experimental groups (stone formers) and control group (non-stone formers) are compared and the advantages and disadvantages of each method are discussed. Disclosure: No significant financial interest or other affiliations with a funding organization or with a commercial supporter of the session and/or provider of commercial services exists.

methods; titratable method; seed method; inhibitory potential

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