Stone formation and urine composition in calcium stone formers without medical treatment.

A retrospective estimate of the annual rate of stone formation (fSF) was obtained in only 154 (35%) of 438 patients without medical treatment at our out-patient stone clinic. Eighty-three of these patients had never been on any prophylactic treatment and were only given advice concerning drinking and dietary habits. There was a high calcium excretion in 46%, high oxalate in 17%, low citrate in 11%, low magnesium in 17%, and increased urate in 16% of the patients. As much as 25% had a 24-hour urine volume below 1,000 ml. There was a good correspondence between stone formation during the follow-up period (tT) and a period of the same length following diagnosis (tA). The mean (+/- SD) tT was 3.2 +/- 1.9 years, with an fSF of 0.19 +/- 0.43. During the tA period fSF was 0.13 +/- 0.31. The number of patients who formed new stones during these periods were 21 and 22, respectively. It is suggested that stone formation during tT and tA advantageously might be used for preliminary evaluation of the therapeutic response. The risk of forming a urine highly supersaturated with calcium oxalate was expressed in terms of a standardized AP(CaOx) index calculated for a 24-hour urine volume of 1,500 ml. There was no relationship between this AP(CaOx) index and fSF. When only those patients were considered who formed new stones during the first 10 years after diagnosis, slightly higher values of the standardized AP(CaOx) index were recorded than in the recurrence-free group.(ABSTRACT TRUNCATED AT 250 WORDS)