Struvite stones: Long term follow up under metaphylaxis

This study presents the results of a 10-year metaphylaxis of 19 former struvite stone formers, each having had 2-3 stone operations. In these patients, urine was acidified with L-methionine (Acimethin(R)) using a dose of three to six tablets 500 mg/day. Every three months, 11 laboratory parameters were checked in 24-hour urine. 6 parameters were determined in serum. In addition, urine samples were tested for infection. Statistical analysis of analytical data, which was supported by computer graphs, provided the results for the urinary parameters. They were described by geometric means and 95% confidence intervals using ANOVA (analysis of variance). During therapy, the mean pH values decreased significantly from 7.5 to 5.5. Significant increases were found in the excretion of citrate, magnesium, potassium and uric acid. An increase was also found for calcium, which, however, could not be confirmed to be statistically significant (p = 0.08). In serum, changes of parameters could only be registered for calcium and phosphate. However, at all times, total serum concentrations stayed within their normal limits. Three patients suffered occasional infections (16 %), only two of them formed recurrent stones (10 %). In assessing the efficacy of L-methionine therapy, the drop in urinary pH to acidic values was the most relevant factor for metaphylaxis.