The structure of canine urinary calculi

Thin sections of canine calculi were examined using microradiographic techniques and although nuclei were detected in a few stones, their presence did not appear to be necessary for the formation of canine calculi. Concentrically arranged laminar bands were seen in the majority of magnesium ammonium phosphate calculi, but radial striation was seen only in one stone which was composed of ammonium urate. Fissures were observed in the centres of several calculi composed of magnesium ammonium phosphate.