A US study was recently undertaken to see whether a high-tech hydration programme – complete with smart water bottles, reminders, coaching and even financial incentives – could help people drink enough water to stop stones from coming back, with the findings published in The Lancet.
A large clinical trial led by the Urinary Stone Disease Research Network and co-ordinated by the Duke Clinical Research Institute set out to answer a key question: can a structured behavioural programme help people drink enough fluids to prevent kidney stones from returning?
The findings shed light on why preventing kidney stones remains difficult, even when people are motivated and receive ongoing support.
"The trial results show that despite the importance of high fluid intake to prevent stone recurrence, achieving and maintaining very high fluid intake is more challenging than we often assume for people with urinary stone disease," said Charles Scales, MD, corresponding and co-senior author of the paper and Associate Professor in the departments of Urology and Population Health Sciences at Duke University School of Medicine.
“The challenge of adherence probably contributes to the relatively high rate of stone recurrence in people with this chronic condition,” he said.
Smart bottles and coaching still fell short
Participants in the study were randomly assigned to either standard care or a behavioural hydration programme designed to increase fluid intake. The programme included Bluetooth-enabled smart water bottles that tracked how much participants drank, along with personalised hydration goals (“fluid prescriptions”), reminder texts, financial incentives, and health coaching.
Each participant’s “fluid prescription” was calculated by comparing their usual urine output with the amount needed to reach a daily goal of at least 2.5 litres.
Although people in the programme did increase how much they drank, and their average urine output rose, the improvement was not enough to significantly reduce the rate of symptomatic kidney stone recurrence across the entire group.
Largest behavioural study of its kind
The trial included 1 658 adolescents and adults from six major clinical centres. Researchers followed participants for two years to monitor outcomes.
This study stands out because it directly measured whether kidney stones came back, rather than focusing only on fluid intake or urine levels. Researchers used regular surveys and imaging to determine if new stones formed or existing ones grew.
Why staying hydrated is so difficult
The results highlight how hard it can be for people to consistently drink large amounts of fluid every day, even when supported by technology and coaching. The findings suggest that a single hydration target may not work for everyone, since fluid needs vary depending on factors such as age, body size, lifestyle, and overall health.
“Across adolescents and adults, the study moves the field toward more precise prevention,” said Gregory Tasian, MD, co-senior author and attending paediatric urologist in the Division of Urology and principal investigator of the trial at the Children’s Hospital of Philadelphia.
“Rather than asking every patient to meet the same fluid goal, we should determine who benefits from which targets, understand why adherence breaks down, and build interventions – behavioural and medical – that reliably reduce stone recurrence,” he said.
Toward more personalised kidney stone prevention
Researchers say the findings point to the need for new approaches to prevention. These could include more individualised hydration goals, strategies to overcome barriers related to work and daily routines, and potential treatments that help keep minerals dissolved in the urine.
“Kidney stone disease is a chronic condition, punctuated by unpredictable, sometimes excruciatingly painful episodes that can disrupt work, sleep, productivity and life in general,” said Alana Desai, MD, first author of the study and principal investigator at the Washington University in St Louis study site.
“Most people would appreciate a simple means to reduce their chances of experiencing another event.”
The study, along with other research from the Urinary Stone Disease Research Network, was funded by the National Institute of Diabetes and Digestive and Kidney Diseases.
Study details
Prevention of urinary stones with hydration: a randomised clinical trial of an adherence intervention
Alana Desai, Naim Maalouf, Jonathan Harper et al.
Published in The Lancet on 21 March 2026
Summary
Background
Increased 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.
Methods
In 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.
Findings
Between 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.
Interpretation
A 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 two-year follow-up period.
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