Presentation Authors: Joshua Bernard*, Lihai Song, Brittney Henderson, Philadelphia, PA, Steven Warner, San Diego, CA, Gregory Tasian, Philadelphia, PA
Introduction: Maintaining a high urine output is important to decrease kidney stone recurrence. However, the precise relationship between fluid intake and urine output is unknown and data to support clinical recommendations for water intake to reach urine output goals are lacking. We developed a model to estimate the change in 24-hour urine volume from daily water intake volume among adolescents with kidney stones.
Methods: We conducted a secondary analysis of data collected as part of the Barriers to Water Intake study, which examined daily water intake habits of 25 adolescents with nephrolithiasis. Over 7 days, participants used smart water bottles to self-monitor and record water intake. Twenty-four hour urine volumes from 12 months before and after the study period were collected via chart review for each participant. Participants' locations were obtained from mobile devices and were used to ascertain daily local wet bulb temperature for each participant during the study period. A linear regression model with a random intercept for each participant was fit to estimate the association between daily water intake and 24-hour urine volume, adjusting for age, sex, race, and daily mean wet-bulb temperature.
Results: Within 12 months of the study period, 22 participants had a total of 57 24-hour urine collections obtained. Median daily water intake was 1.4 L (IQR 0.67-1.94). Median 24-hour urine volume was 2.01 L (IQR 1.20-2.73). A 1 L increase in daily water intake was associated with a 0.71 L increase in 24-hour urine output (95% CI 0.55-0.87, p < 0.001). Applied to a hypothetical patient who needs to increase their 24-hour urine volume by 550 mL to reach a goal of 2.5 L, a clinician can recommend increasing daily water intake by 775 mL.
Conclusions: A 1 L increase in water intake increased 24-hour urine volume by 710 mL. These results can be used to develop fluid intake "prescriptions" to help adolescents with kidney stones achieve urine output goals to decrease kidney stone recurrence.
Source of Funding: K23DK106428