A coaching push to drink more water did not cut kidney-stone recurrences

"Drink more water" is the most universal advice given to people who have had a kidney stone, and it rests on sound logic: dilute urine is less likely to crystallise into a stone. The trouble has never been the theory but the follow-through — keeping fluid intake high, day after day, for years. A large randomised trial set out to test whether an intensive programme built to solve exactly that adherence problem could turn higher water intake into fewer stones. It could raise the water intake. It did not deliver fewer stones [s1].

The PUSH trial (Prevention of Urinary Stones with Hydration) enrolled participants aged 12 years and older who had a history of urinary stone disease and low 24-hour urine volumes by current guidelines — the group in whom more fluid is most likely to help [s1]. It ran at six academic medical centres in the United States and randomly assigned participants 1:1 to either a multicomponent behavioural intervention or a control group receiving guideline-concordant care [s1]. Investigators, treating physicians, outcome assessors, and adjudicators were all masked to group assignment [s1].

What the programme did

This was not a leaflet. The intervention combined a specific fluid prescription, financial incentives for adhering to it, health coaching to work through the barriers that stop people drinking more, and patient-selected tools such as text-message reminders to keep intake up [s1]. The primary outcome was symptomatic stone recurrence — a stone passing or a procedure needed for stones — over a two-year follow-up, analysed by intention to treat [s1]. Secondary outcomes included the change in 24-hour urine volume, urinary symptoms, radiographic stone recurrence or growth, and a composite of symptomatic recurrence, new stone formation, and growth of existing stones [s1]. The prespecified safety endpoint was hyponatraemia — dangerously low blood sodium — requiring hospitalisation, the plausible downside of pushing people to drink much more [s1]. The trial is registered as NCT03244189 [s2].

What it showed

Between 26 October 2017 and 18 February 2022, 1,658 participants were randomly assigned — 826 to the intervention and 832 to control [s1]. The median age was 44 years (interquartile range 29 to 59), 946 (57%) were female, and 1,104 (66.6%) were recurrent stone formers [s1]. At a median follow-up of 738 days, symptomatic stone events occurred in 154 participants (19%) in the intervention group and 165 (20%) in the control group — a hazard ratio of 0.96 (95% confidence interval 0.77 to 1.20) [s1]. That interval sits squarely across 1.0: no detectable difference.

The intervention did do what it was designed to do at the level of behaviour. Twenty-four-hour urine volume rose from baseline in both groups and was higher in the intervention group at 6, 12, 18, and 24 months [s1]. So the programme succeeded in getting people to drink and produce more urine — it simply did not translate that into fewer stones. There was no difference between groups in stone growth of at least 2 mm or in new stones on imaging, and the composite outcome was likewise not statistically different [s1].

The extra fluid was not free of nuisance. Urinary storage symptoms — frequency, urgency, and waking at night to urinate — were greater in the intervention group than in control at 6 and 12 months, though not at later timepoints [s1]. On the safety side the news was reassuring: no episodes of hyponatraemia required hospitalisation, and asymptomatic low sodium was uncommon, in 12 participants (1%) in the intervention group versus 2 (under 1%) in control [s1].

How to read a null result

A trial like this is easy to misread as debunking hydration itself. It does not. It tested whether an intensive adherence programme layered on top of usual care changes outcomes, and within its two-year window the answer was no — even though urine volume genuinely rose. Two years may simply be too short for a modest shift in urine dilution to show up as fewer stones, which form slowly; the recurrence curves could still diverge later. And usual care in the trial was guideline-concordant, meaning the comparison group was already being told to drink more, narrowing the room for an add-on to prove itself.

What to watch

PUSH was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and sponsored by Duke University — an independent, publicly funded trial with no product to sell [s1][s2]. Its honest conclusion is that a behavioural programme to promote fluid intake did not reduce recurrent stone events, but modestly increased urine volume, over two years [s1]. The finding does not overturn the basic advice to stay well hydrated; it tempers the expectation that a costly, structured coaching programme will, on its own, keep stones from coming back. The open question is whether a longer horizon, or a different target than fluid alone, changes the picture.

Sources

• [s1] Prevention of urinary stones with hydration: a randomised clinical trial of an adherence intervention. The Lancet. 19 March 2026. doi:10.1016/S0140-6736(25)02637-6. PMID 41864748.
• [s2] ClinicalTrials.gov. Prevention of Urinary Stones With Hydration (PUSH), NCT03244189. U.S. National Library of Medicine.