A major clinical trial has upended conventional wisdom about kidney stone prevention: simply drinking more water, even with intensive coaching and financial incentives, does not significantly reduce the risk of painful kidney stones returning. The findings suggest that current hydration-based prevention strategies may be insufficient for many patients, even when they successfully increase urine output.

What Did the PUSH Trial Actually Test?

Researchers at Washington University in St. Louis conducted the Prevention of Urinary Stones with Hydration (PUSH) trial, enrolling 1,658 adolescents and adults with a history of kidney stones and low baseline urine volumes . About two-thirds of participants were recurrent stone formers, meaning they had experienced multiple episodes. The study randomly assigned 826 people to an intensive behavioral intervention and 832 to standard guideline-concordant care, then tracked them for a median of 738 days, or roughly two years.

The intervention was comprehensive and went far beyond simple advice to drink more water. Participants received personalized "fluid prescriptions" tailored to their individual needs, financial incentives to encourage adherence, health coaching from specialists, and optional text message reminders. When people struggled to comply, researchers used tailored problem-solving interventions to address barriers. Despite these intensive efforts, the results were striking.

Why Did Increased Hydration Fail to Prevent Kidney Stones?

Over the study period, symptomatic kidney stone events occurred in 154 people (19%) in the intervention group and 165 people (20%) in the control group, indicating no significant difference in recurrence risk . Even more puzzling, the intervention group achieved measurable improvements in urine volume at months 6, 12, 18, and 24, yet these gains did not translate into fewer kidney stones. There were also no between-group differences in new stone formation, stone growth of at least 2 millimeters, or the combined outcome of recurrence, growth, or new stones.

The researchers noted that adherence challenges persisted even with intensive support, and subgroup analyses showed no heterogeneity of treatment effect by age, sex, or adherence level. Notably, even among participants who achieved the target urine output of at least 2.5 liters per day, kidney stone recurrence rates remained unchanged. This suggests that simply increasing fluid intake, even when objectively achieved, may be insufficient to meaningfully alter recurrence risk in a broad population.

"The results of the PUSH study do not undermine the importance of increasing fluid intake for stone prevention, as this remains a low-cost, low-risk intervention with likely benefits based on previous literature. Rather, our study suggests that although contingency management intervention with health coaching for non-adherent participants was insufficient to yield significant clinical benefit, relative to participants in the control group, future investigations could apply optimization study designs," explained Dr. Alana Desai and colleagues.

Dr. Alana Desai, Washington University in St. Louis

What Are the Implications for Kidney Stone Prevention?

The PUSH trial findings stand in contrast to some earlier research. A systematic review of 26 randomized controlled trials and 5 non-randomized studies published in the Annals of Internal Medicine found low-strength evidence that increased water intake, dietary modification, and pharmacologic therapies such as thiazide diuretics, alkali treatment, and allopurinol may reduce recurrence in calcium-oxalate or calcium-phosphate kidney stones . However, the risk of bias in those studies was high, and the evidence remains uncertain for many interventions.

The disconnect between the PUSH trial and earlier literature suggests that kidney stone prevention is more complex than previously understood. Factors beyond hydration alone, such as diet composition, genetic predisposition, metabolic disorders, and individual urinary chemistry, may play crucial roles in determining who develops recurrent stones. The fact that some people develop kidney stones despite adequate hydration while others never form them despite low fluid intake points to underlying biological differences that hydration alone cannot address.

How to Approach Kidney Stone Prevention Today

• Maintain Adequate Hydration: While the PUSH trial showed that increased hydration alone did not prevent recurrence, experts still recommend maintaining adequate fluid intake as a low-cost, low-risk intervention with potential benefits based on previous research and physiological principles.
• Combine Hydration with Dietary Changes: Focus on reducing sodium intake, limiting animal protein consumption, and managing calcium and oxalate intake based on your specific stone type, as dietary modification may offer additional benefits beyond hydration alone.
• Consider Pharmacologic Options: Discuss with your nephrologist or urologist whether medications such as thiazide diuretics, potassium citrate, or allopurinol may be appropriate for your individual risk profile and stone composition.
• Get Metabolic Testing: Undergo comprehensive metabolic evaluation to identify underlying disorders such as hyperparathyroidism, hypercalciuria, or hyperuricemia that may require targeted treatment beyond lifestyle modifications.
• Monitor Urine Chemistry: Regular 24-hour urine collections can help assess whether your interventions are actually changing the chemical environment that promotes stone formation, rather than relying solely on symptom absence.

The PUSH trial also documented some side effects worth noting. Urinary storage symptoms, including frequency and urgency, modestly increased in the intervention group at months 6 and 12, though these differences were not sustained. Additionally, asymptomatic hyponatremia, a condition where sodium levels drop dangerously low, was more frequent in the intervention group at 1% compared to less than 1% in the control group, though no cases required hospitalization .

For patients with recurrent kidney stones, the takeaway is clear: hydration remains a reasonable first step, but it should not be the only strategy. Working closely with a nephrologist or urologist to identify the specific type of kidney stone you form, understanding your individual risk factors, and pursuing targeted dietary or pharmacologic interventions tailored to your condition offers a more promising path forward than relying on hydration alone. The PUSH trial demonstrates that one-size-fits-all prevention strategies, no matter how well-intentioned or intensively supported, may not work for everyone.