[The influence of uric acid on the calcium oxalate stone formation (author's transl)]

Statistic analysis of data from 209 calcium oxalate stone patients and 42 stone-free patients pertinent to the concentration and excretion of uric acid in urine and of uric acid levels in the serum yielded no significant difference between the two groups. Only 17% of the calcium oxalate stone patients suffered from hyperuricuria and hyperuricemia was found only in 15% of these patients. Based on these findings, our in-vitro experiments as to the influence of uric acid on calcium oxalate stone formation yielded the following results: firstly, precipitates in urine form only at uric acid concentrations which in-vivo are rate exceptions humans, and secondly, the precipitates at pH 5.5--6.0 always contain uric acid, and a precipitation of calcium oxalate only is never observed. From the experiments one has to conclude that there exists no "salting-out effect" of uric acid on calcium oxalate in urine but rather that precipitate formation reflects the individual solution- and crystallization characteristics of the precipitating compounds.