Prevention of urinary stones with hydration: a randomised clinical trial of an adherence intervention.

backgroundIncreased fluid intake is universally recommended to decrease the risk of recurrent urinary stones; however, adherence is challenging. The effectiveness of interventions to maintain high fluid intake has not been well studied. We sought to determine whether a multicomponent behavioural intervention programme to promote high fluid intake reduces symptomatic stone recurrence, compared with a control.

methodsIn this randomised clinical trial, participants aged 12 years and older with a history of urinary stone disease and low 24 h urine volumes based on current guidelines were enrolled at six academic medical centres in the USA. Participants were randomly assigned in a 1:1 ratio to a multicomponent behavioural intervention designed to promote increased fluid intake or to the control group receiving guideline-concordant care. The intervention consisted of a fluid prescription, financial incentives to adhere to fluid prescription, health coaching to overcome barriers to consuming more fluids, and patient-selected approaches such as text messaging to maintain increased fluid intake. Randomisation assignment was computer-generated remotely, and investigators, treating physicians, outcome assessors, and adjudicators were masked to group assignment. The primary outcome was symptomatic stone recurrence defined as stone passage or procedural intervention for stone(s) during a 2-year follow-up period, analysed in the intention-to-treat population. Secondary outcomes included change in 24 h urine volume, urinary symptoms, radiographic stone recurrence or growth, and a composite outcome of symptomatic stone recurrence, new stone formation, and growth of existing stone(s); hyponatremia requiring hospitalisation was the safety endpoint. This trial is registered with ClinicalTrials.gov, NCT03244189.

findingsBetween Oct 26, 2017, and Feb 18, 2022, 1658 participants were randomly assigned to intervention (n=826) and control (n=832) groups (median age 44 years [IQR 29-59]; 946 [57%] female). At a median follow-up of 738 days (IQR 711-778), symptomatic stone events occurred in 154 (19%) participants in the intervention group and 165 (20%) in the control group (hazard ratio 0·96, 95% CI 0·77-1·20). Among these 1658 participants, 1104 (66·6%) were recurrent stone formers. 24 h urine volume increased from baseline in both groups and was higher in the intervention group at months 6, 12, 18, and 24 compared with the control group. Urinary storage symptoms of frequency, urgency, and nocturia were greater in the intervention group versus control at months 6 and 12 but not at other timepoints. There was no difference in stone growth of at least 2 mm or new stones between groups from baseline to end-of-study imaging, and the composite outcome of symptomatic stone recurrence, new stone formation, or stone growth of at least 2 mm was also not statistically different between groups. No episodes of hyponatremia requiring hospitalisation (safety endpoint) were reported; 12 (1%) participants in the intervention group had asymptomatic hyponatraemia versus two (<1%) participants in the control group.

interpretationA behavioural intervention programme to promote fluid intake for secondary stone prevention did not reduce recurrent stone events but modestly increased urine volume compared with guideline-based care during a 2-year follow-up period.

fundingNational Institute of Diabetes and Digestive and Kidney Diseases.