URINARY VOLUME, WATER AND RECURRENCES IN IDIOPATHIC CALCIUM NEPHROLITHIASIS - A 5-YEAR RANDOMIZED PROSPECTIVE-STUDY

Purpose: We define the role of urine volume as a stone risk factor in idiopathic calcium stone disease and test the actual preventive effect iveness of a high water intake. Materials and Methods: We studied 101 controls and 199 patients from the first idiopathic calcium stone epis ode. After a baseline study period the stone formers were divided by r andomization into 2 groups (1 and 2) and they were followed prospectiv ely for 5 years. Followup in group 1 only involved a high intake of wa ter without any dietetic change, while followup in group 2 did not inv olve any treatment. Each year clinical, laboratory and radiological ev aluation was obtained to;determine urinary stone risk profile (includi ng relative supersaturations of calcium oxalate, brushite and uric aci d by Equil 2), recurrence rate and mean time to relapse. Results: The original urine volume was lower in male and female stone formers compa red to controls (men with calcium oxalate stones 1,057 +/- 238 ml./24 hours versus normal men 1,401 +/- 562 ml./24 hours, p <0.0001 and wome n calcium oxalate stones 990 +/- 230 ml./24 hours versus normal women 1,239 +/- 440 ml./24 hours, p <0.0001). During followup recurrences we re noted within 5 years in 12 of 99 group 1 patients and in 27 of 100 group 2 patients (p = 0.008). The average interval for recurrences was 38.7 +/- 13.2 months in group 1 and 25.1 +/- 16.4 months in group 2 ( p = 0.016). The relative supersaturations for calcium oxalate, brushit e and uric acid were much greater in baseline urine of the stone patie nts in both groups compared to controls. During followup, baseline val ues decreased sharply only in group 1. Finally the baseline urine in p atients with recurrences was characterized by a higher calcium excreti on compared to urine of the patients without recurrences in both group s. Conclusions: We conclude that urine volume is a real stone risk fac tor in nephrolithiasis and that a large intake of water is the initial therapy for prevention of stone recurrences. In cases of hypercalciur ia it is suitable to prescribe adjuvant specific diets or drug therapy .