Largest study of its kind tests hydration strategy for kidney stones

Kidney stones can cause some of the most intense pain people ever experience, affecting daily life and leading many to hospital emergency visits. It affects 1 in 11 people in the U.S., and almost half will experience a recurrence.

A major new study from the Urinary Stone Disease Research Network, coordinated by the Duke Clinical Research Institute, tested whether a behavioral program could help people drink enough fluids to prevent stones from coming back.

The study, published in The Lancet on March 19, provides important new insights into why preventing kidney stones is so challenging, even with strong motivation and daily 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, M.D., 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 likely contributes to the relatively high rate of stone recurrence in people with this chronic condition,” Scales said.

Participants were randomly assigned to receive the standard care or to participate in a behavioral hydration program. The program used Bluetooth-enabled smart water bottles that measured fluid intake, personalized hydration goals (“fluid prescriptions”), financial incentives, reminder texts, and health coaching to encourage people to drink more fluids.

The “fluid prescription” was determined by comparing how much urine a participant typically makes with how much more water they needed to drink to reach a urine output goal of at least 2.5 liters a day.

People in the program did hydrate more, increasing their average urine output, but the increase wasn’t large enough to lower the rate of symptomatic kidney stone recurrence across the overall group.

The trial enrolled 1,658 adolescents and adults at six U.S. clinical centers (UT Southwestern Medical Center, Washington University in St. Louis, University of Pennsylvania/Children’s Hospital of Philadelphia, University of Washington, Mayo Clinic and Cleveland Clinic), making it the largest behavioral study ever conducted for kidney stone prevention. Scientists followed trial participants for two years after enrollment to collect data.

Researchers noted that the study’s design was the first to measure actual stone recurrence, as opposed to fluid intake or urine output, and used regular surveys and imaging to track whether new stones formed or existing stones grew.

Together, the findings highlight how difficult it is for many people to drink large amounts of fluid every day, even with structured support. Researchers said it raises questions about the potential need for hydration targets that are more individually tailored, since each person’s hydration needs may differ based on age, size, lifestyle, and health conditions.

“Across adolescents and adults, the study moves the field toward more precise prevention,” said Gregory E. Tasian, M.D., co-senior author and attending pediatric 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 — behavioral and medical — that reliably reduce stone recurrence,” Tasian said.

Researchers said this evidence underscores the need to explore new ways to prevent stones, including tailored hydration targets, strategies to overcome hydration barriers created by work and lifestyle, and potential therapies to 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, M.D., 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,” said Desai.

Reference:

Desai A, Maalouf N, Harper J et al., Prevention of urinary stones with hydration: a randomised clinical trial of an adherence intervention, The Lancet, DOI:10.1016/S0140-6736(25)02637-6