Normal calcium oxalate crystal growth inhibition in severe calcium oxalate nephrolithiasis

Urine from mammalian kidneys is regularly supersaturated with respect to calcium oxalate monohydrate, the most common solid phase in human nephrolithiasis, and also inhibits the nucleation, growth, and aggregation of calcium oxalate crystals. Nephrolithiasis is often associated with increased supersaturation, and it is assumed that this increase overbalances the inhibition effects, causing stones. However, some patients form stones in the absence of increased supersaturation, and in those patients, one might assume that reduced inhibition is the cause of their stones. This hypothesis was tested in 25 patients who formed at least ten stones each, yet lacked the usual metabolic abnormalities that increase supersaturation. Compared with 25 age- and sex-matched control subjects, urine supersaturation among the patients was not increased; this is an expected result of this study's selection criteria. Compared with the same age- and sex-matched control subjects, urine from the patients showed no evidence for reduced inhibition of calcium oxalate crystal growth, so low inhibition of growth did not contribute to pathogenesis of stones in our highly selected study population, despite their otherwise unexplained and active stone formation. These results do not support the hypothesis that growth inhibition defects are a cause of stone disease.