Nephrology · Medical Literature
[Correspondence] PUSH trial limits: why fluids still matter
Abstract
We read with interest the Article1 by Alana C Desai and colleagues on the results of the well designed, large-scale Prevention of Urinary Stones with Hydration (PUSH) trial, which evaluated a multicomponent intervention to improve fluid intake and idiopathic urinary stone recurrence in adolescents and adults. Both the Article and the related Comment2 concluded that increasing daily urinary volume failed to reduce stone recurrence; therefore, alternative prevention strategies beyond solely increasing fluid intake should be sought.
Clinical relevance
Do the results of the PUSH trial—showing that a multicomponent behavioral intervention failed to reduce symptomatic stone recurrence despite increased urinary volume—justify abandoning fluid intake as a cornerstone of idiopathic urinary stone prevention? __SNAPSHOT__ {"studyDesign":"Correspondence (letter to the editor) commenting on a previously published randomized controlled trial (PUSH trial, Desai et al., The Lancet, March 2026). This publication contains no original data.","setting":"Not applicable (correspondence); the referenced PUSH trial was conducted at six academic medical centers in the United States.","sampleSize":"Not applicable (correspondence). The referenced PUSH trial enrolled n=1,658 (intervention: n=826, control: n=832).","population":"Not applicable (correspondence). The referenced PUSH trial enrolled adolescents and adults aged ≥12 years with a prior history of idiopathic urinary stone disease and low baseline 24-hour urine volumes.","intervention":"Not applicable (correspondence). The referenced PUSH trial tested a multicomponent behavioral intervention including personalized fluid prescriptions, financial incentives, health coaching, and optional text message reminders to promote increased fluid intake.","comparator":"Not applicable (correspondence). The referenced PUSH trial comparator was guideline-concordant usual care.","primaryOutcome":"Not applicable (correspondence). The referenced PUSH trial primary endpoint was symptomatic stone recurrence (stone passage or need for procedural intervention) over 24 months of follow-up.","followUp":"Not applicable (correspondence). The referenced PUSH trial follow-up was 24 months (median 738 days).","fundingSource":"Not reported for the correspondence. The referenced PUSH trial was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health."}
Key findings
This correspondence contains no original data, effect sizes, confidence intervals, or p-values. All quantitative findings cited below derive from the referenced primary PUSH trial (Desai et al., The Lancet, 2026) and publicly reported secondary analyses presented at AUA 2026, not from the correspondence itself. In the PUSH trial, symptomatic stone recurrence occurred in 19% of the intervention group versus 20% of the control group (HR 0.96; 95% CI 0.77–1.20), indicating no statistically significant difference. The behavioral intervention modestly increased 24-hour urine volume at months 6, 12, 18, and 24, but these gains did not translate into reductions in symptomatic recurrence, new stone formation, stone growth ≥2 mm, or a composite stone outcome. Asymptomatic hyponatremia was more frequent in the intervention group (1% vs. <1%; p=0.018), though no hospitalizations for hyponatremia occurred. A secondary analysis (Harper et al., AUA 2026) found that patients who maintained higher urine volumes from baseline through follow-up had a significantly lower risk of symptomatic stone recurrence (adjusted HR 0.51; 95% CI 0.31–0.83; p<0.01), and that a median net increase in urine volume of 438 mL/day was associated with a 24% lower likelihood of combined symptomatic or radiographic recurrence (OR 0.76; 95% CI 0.59–0.98; p=0.04), even without reaching the 2.5 L/day guideline target. NNT is not calculable from the correspondence itself. The correspondence authors' central argument—that fluid intake remains important despite the null primary trial result—is an interpretive position, not a novel data analysis.
Practice implications
This correspondence is a brief interpretive commentary, not an original study; no independent clinical conclusions can be drawn from it beyond the opinion of its authors. The authors challenge the interpretation—advanced in both the primary PUSH article and its accompanying Comment—that the negative primary outcome should prompt clinicians to abandon fluid intake as a prevention strategy. The PUSH trial established that a contingency management behavioral intervention with health coaching was insufficient to significantly reduce symptomatic stone recurrence compared to guideline-based care over two years, even when urine volume modestly increased. The trial did not establish that increasing fluid intake per se is ineffective for stone prevention; rather, it demonstrated that this specific behavioral program failed to yield clinical benefit at the population level. Critically, the trial enrolled only patients with low baseline urine volumes at academic US centers, limiting generalizability to patients who are already adherent to hydration recommendations, to those with non-idiopathic stone disease, and to non-academic or non-US settings. The secondary analyses (not in the correspondence but relevant to its argument) suggest that sustained, meaningful increases in urine volume may still confer protection, and that urine osmolality may add prognostic value. Clinicians should resist concluding that fluid counseling is futile; the PUSH trial tested an adherence intervention, not the biologic effect of hydration itself. Equally, the null primary result should temper enthusiasm for resource-intensive behavioral programs as standalone prevention strategies. Available evidence supports fluid intake as a low-cost, low-risk cornerstone of stone prevention, but underscores that adherence remains a major barrier and that dietary and pharmacological adjuncts likely need to be incorporated. Because this is a correspondence rather than a primary study, it is restricted to the abstract and letter text; the full argument of the authors may contain nuances not captured here. __LIMITATIONS__ 1. Publication type: This is a correspondence letter, not an original study. It contains no independent data, statistical analyses, or new patient-level evidence; conclusions are the authors' interpretive opinions. 2. Abstract-only review: Only the abstract of the correspondence was available for this summary, which limits full assessment of the authors' complete argument and the evidence they cite. 3. Inherited limitations from the referenced PUSH trial: The primary trial enrolled only patients with low baseline urine volumes, limiting applicability to adherent patients; neither group achieved the guideline-recommended 2.5 L/day target (median achieved 1.8 L/day), raising concerns about whether the intervention was sufficiently potent to test the hydration hypothesis; blinding of participants was not feasible given the behavioral nature of the intervention, introducing performance bias risk; the trial was conducted exclusively at six US academic centers, limiting generalizability; subgroup and sensitivity analyses showed no heterogeneity of treatment effect even among those achieving ≥2.5 L/day, though this analysis was exploratory. 4. Risk of misinterpretation: The correspondence itself notes that the original article and its Comment may have led clinicians to over-interpret the null primary result as evidence against fluid intake broadly, rather than against this specific behavioral adherence program. __BOTTOM_LINE_CATEGORY__ potentially_practice_informing __BOTTOM_LINE__ The PUSH trial demonstrated that a multicomponent behavioral adherence intervention modestly increased urine volume but failed to reduce symptomatic stone recurrence over two years; this correspondence argues this null result should not be interpreted as evidence that fluid intake is unimportant for stone prevention. Clinicians should maintain fluid intake counseling as a foundational, low-risk prevention strategy while recognizing that intensive adherence programs alone are insufficient and that adjunctive dietary and pharmacological approaches should be incorporated for appropriate patients. This correspondence adds interpretive context rather than new evidence and should be read alongside the primary PUSH trial results and its AUA 2026 secondary analyses.