[Relationships between diuresis, urine pH and lithogenesis].

Although an increased water intake is suitable in the pathophysiology and treatment of renal lithiasis, less attention is given to changes caused by water diuresis on urinary pH. The objective of this study was to show the relationship between urinary flow and pH. On two consecutive days, at the beginning and end of a four-hour interval starting at 8:00 am, volume and pH in urine, as well as plasma osmolality, haematocrit and protein concentrations were measured; all specimens were collected under normal conditions except for those collected on the second day at noon, which were collected after a water load equivalent to 1.5% body weight taken between 8:00 and 9:00 am. A decrease in serum osmolality, haematocrit and protein concentrations was noted. Urinary pH changes were different based on baseline values. Baseline urine pH values lower than or equal to 5.8 resulted in increased values, while baseline values greater than or equal to 6.5 gave decreased values. Mean increase in pH as a result of greater water intake was 0.57 units.