A multicomponent behavioral intervention designed to increase fluid intake did not reduce symptomatic kidney stone recurrence compared with guideline-based care, despite modestly increasing urine volume over 2 years in a randomized clinical trial.
In the Prevention of Urinary Stones with Hydration trial, researchers randomly assigned 1,658 patients aged 12 years and older with urinary stone disease and low baseline urine volume to a behavioral intervention or usual care across six US academic centers. Both groups received guideline-based care and a Bluetooth-enabled smart water bottle, while the intervention group additionally received individualized fluid prescriptions, financial incentives, health coaching, and optional supports such as text messaging.
The primary outcome was symptomatic stone recurrence over 24 months, defined as stone passage or stone-related procedural events.
At a median follow-up of 738 days, symptomatic stone events occurred in 19% of patients in the intervention group vs 20% in the control group, with no significant difference between groups. Kaplan-Meier estimates at 2 years were 20% vs 21%, respectively. Subgroup analyses showed no differences by sex, age, clinical center, or provider, and adherence analyses were similarly null.
The cohort had a median age of 44 years, and 57% were female; 67% were recurrent stone formers. Baseline 24-hour urine volume was 1.30 L per day in adults and 0.85 L per day in adolescents.
Urine volume increased from baseline in both groups and remained higher in the intervention group at 6, 12, 18, and 24 months. Among adults, urine volume increased by approximately 600 mL per day in the intervention group vs 360 mL per day in the control group, although the between-group difference diminished over time.
Secondary outcomes, including stone growth of at least 2 mm, new stone formation, and a composite imaging outcome, were similar between groups.
Urinary storage symptoms, including frequency, urgency, and nocturia, were more common in the intervention group at 6 and 12 months but not at later timepoints.
No episodes of hyponatremia requiring hospitalization were reported. Asymptomatic hyponatremia occurred in 1% of patients in the intervention group vs less than 1% in the control group.
The primary outcome was analyzed in the intention-to-treat population using time-to-event methods, and 24-hour urine volume was assessed using repeated-measures mixed-effects models. Sensitivity analyses excluding early events and procedures for asymptomatic stones did not change the findings.
Participants were recruited from tertiary care centers, which may limit generalizability. The authors also noted that urine volume increased substantially in the control group, possibly due to specialty care and frequent participant contact, which may have reduced the detectable difference between groups. Additional fluid intake not captured by the smart water bottle was not measured.
“Participants in the behavioural intervention group achieved a greater urine volume compared with participants in the control group. However, this increase in urine volume did not result in a decrease in recurrent symptomatic stone events over 2 years of follow-up,” the researchers wrote.
The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases. Disclosures for the researchers are reported in the original publication.
Source: The Lancet
