Orotic acid sodium salt in kidney stones and urinary deposits

Kidney stones from a plaice, Pleuronectes platessa, have been shown to consist of the sodium salt of orotic acid. Precipitation of orotic acid in human kidneys and urine samples has previously been reported but the precipitates must have been salts, most likely the sodium salt, of orotic acid and not the free acid. This reinterpretation is based on the acid strength of orotic acid and on data for the solubilities of sodium orotate and orotic acid. Sodium orotate is therefore a member on the list of compounds present in human urinary deposits and calculi. X-ray powder diagrams and d-values and IR-spectra of the sodium salt are recorded to facilitate future identifications.