Abstract The aim of this study was to evaluate 24-h urine volume (UV), estimated osmolarity (eUosm), and Tiselius APCaOx index (TIS) in 181 calcium oxalate stone formers, and the changes achieved in response to the recommendation to reach a UV of at least 2 liters per day, during a follow-up of at least 3 years. Patients of each sex were a posteriori divided into recurrent (R) and non-recurrent (NR) stone formers according to stone events during follow-up. UV, eUosm and TIS were evaluated at baseline (BSL) and End (END). TIS was also determined in first morning urine. Results were compared by two-way ANOVA or chi2. Mean follow-up was 6.8 years. The 24-h osmolar excretion did not differ between R and NR in either sex, and remained stable between BSL and END. UV was significantly lower in R than NR, both at BSL and END, and eUosm was 100–150 mosm/kg H2O higher in R. In both sexes, the increase in UV observed between BSL and END was significantly smaller in R than NR. TIS values were significantly higher in R than NR. They were higher at END than at BSL only in R patients, suggesting a poor compliance of R to drink more. The threshold of TIS for a high risk of crystalluria was found to be 2.45 in both men and women. In conclusion, the patients who showed recurrence of lithiasis not only had lower baseline UV, but were also less able to increase UV than those who did not recur, in spite of recommendations to drink more. Based on preliminary information in the literature, a clinical trial could be designed to evaluate, in these patients, if a low dose of a selective V2 receptor antagonist, increasing their diuresis (and thirst), would prevent new stones.
Bankir et al. (Fri,) studied this question.