Effect of oligomineral water with low sodium and calcium content on urinary parameters of lithogenic risk in patients with kidney stones and high urinary calcium excretion: a pilot study

Background – Water therapy is considered the cornerstone prescription for secondary prevention of nephrolithiasis. However, there is no conclusive evidence in literature about what kind of water obtains the best preventive effect. Oligo-mineral waters have been traditionally favored in this field because of diuretic effect and low calcium content. Some specific types of oligo-mineral waters have also been reported to influence uric acid metabolism by diminishing renal excretion. Aims – The aim of our study was to verify the effect of a 3-day treatment with an oligomineral low-sodium low-calcium water on urinary factors of lithogenic risk in a small cohort of kidney stone formers with hyperuricosuria. Materials and methods – At the Kidney Stone Clinic of Parma University Hospital we consecutively enrolled 10 patients (8 M, 2 F; mean age 47±11 years) with recurrent kidney stone disease and elevated urinary uric acid excretion (> 600 mg/24 h). At the time of enrolment, each patient was prescribed water therapy (with the preferred type of commercial water) as to maintain daily urinary volume above 2 liters and then underwent a 24-hour urinary collection for the determination of urinary profile of lithogenic risk (including sodium, calcium, phosphorus, oxalate, uric acid, magnesium, potassium) without any further dietary advice. Patents were then prescribed a 3-day period on usual diet with the ingestion a low-sodium low-calcium mineral water (courtesy of Acqua&Terme Fiuggi S.U.p.A., Frosinone, Italy) instead of their preferred water. A new 24-hour urinary collection for profile of lithogenic risk was performed during the third day. Results – All patients experienced a decrease in urinary uric acid excretion. The mean decrease was 132±100 mg/24 h. Mean values were 814±133 mg/24 h at baseline and 682±108 mg/24 h (p=0.025) after the 3-day oligomineral water challenge. All other parameters of lithogenic risk showed no significant differences in the two urinary collections. Mean urinary volume was 2,2±0,8 l/24 h at baseline and 2,6±0,6 l/24 h after the intervention (p=0.172). Supersaturation indexes for calcium oxalate, calcium phosphate and uric acid decreased, although not in a significant way (for example, uric acid supersaturation was 3.21±2.83 before and 1.83±1.11 after the intervention, p=0.169). Conclusions – Oligomineral water with low-sodium and low-calcium content seems to have beneficial effects on urinary uric acid excretion, thus may be an useful adjuvant in the medical treatment of nephrolithiasis associated with hyperuricosuria.