Urine volume: Stone risk factor and preventive measure

Background: A high fluid intake is the oldest existing treatment for kidney stones, and, up until a few decades ago, it was the only preventive measure at the physician's disposal for stone recurrences. Methods: Using the data available in literature and partly unpublished personal research, we examine the role of urine volume as a stone risk factor, its impact on calcium crystallization mechanisms and its real importance as a means of prevention. Results: To sum up, the most important findings are: (1) a low urine volume must be considered as a real risk factor, both as regards the onset of renal calculi and stone relapses; (2) an increase in urine volume induced by a high water intake produces favourable effects on the crystallization of calcium oxalate and does not reduce the activity of natural inhibitors; (3) a sufficiently high intake of water and probably other fluids such as coffee, tea, beer and wine has a preventive effect on nephrolithiasis and its recurrence, and (4) the role of fruit juice is still to be defined. Conclusions: A high intake of fluids, especially water, is still the most powerful and certainly the most economical means of prevention of nephrolithiasis, and it is often not used to advantage by stone formers.