Study: Hydration boosted urine, but stone risk unchanged

The first clinical trial to test adherence to a behavioral program designed to increase fluid intake and decrease risk of kidney stones found that participants only modestly increased their urine output. The increased output was not enough to reduce symptomatic stone-recurrence rates, compared with standard care, over the two-year study period. 

The findings, published March 19 in The Lancet, highlight the challenge many people with kidney stones face in drinking the recommended volume of fluids, even with structured support. Study participants, all with a history of kidney stones, had access to “smart” bottles that reminded them to drink water regularly, and received hydration incentives and coaching, as well. 

Kidney stones, objects that form in the kidneys from minerals and salts in the urine, have become increasingly common in the last 20 years, affecting about 1 in 11 people in the United States. The related pain causes significant physical, emotional and financial burdens, especially for those whose stone symptoms reoccur. Increasing fluid intake is universally recommended to reduce recurrence risk.  

“We know hydration is fundamental in reducing kidney stones, but this trial highlights how challenging it may be to change behavior and drink enough to achieve urine-volume goals,” said study co-author Dr. Jonathan Harper, professor of urology at the University of Washington School of Medicine. Harper was the principal investigator of the trial at UW Medicine, which enrolled 309 participants and led remote recruitment efforts nationally during the pandemic. 

The largest behavioral intervention study ever conducted for kidney stone prevention, the trial enrolled 1,658 adults and adolescents across six U.S. academic centers.  

“This study offers the most rigorous evidence to date that simply encouraging or incentivizing people to drink more water may not be sufficient to prevent the recurrence of urinary stones. Our findings suggest that more tailored or innovative approaches may be needed to help reduce recurrence risk,” said first author Dr. Alana Desai, a urologist formerly with UW Medicine who is now on staff at Urology of St. Louis. 

The study used behavior-change principles to try to help people overcome common barriers to consistently following health recommendations.  

Participants in the intervention group were given a Bluetooth-enabled bottle that measured and recorded how much water they drank. They also received financial incentives to encourage meeting a personalized hydration goal, health coaching to identify and overcome obstacles, and supportive measures such as text reminders.  

Instead of just measuring fluid intake and urine output, the researchers intentionally evaluated the most clinically relevant outcome, symptomatic kidney stone recurrence, to determine whether the intervention was effective.  

“Importantly, good hydration is still worth the effort for those prone to kidney stones,” Harper said. “It just may take a different approach to achieve this for everyone.” 

Funding for the trial was provided by the National Institute of Diabetes and Digestive and Kidney Diseases (DK110954) at the National Institutes of Health. 

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