Study Raises New Questions About Achieving Adequate Fluid Intake for Kidney Stones

Urinary stones have been part of the human experience for centuries. Increasing fluid intake as a treatment strategy was first documented in the 17^th century, and remedies to induce urine output were introduced even earlier. With kidney stones on the rise in both children and adults in many parts of the world, experts are investing in research to better understand this ancient medical problem.

A recent study—the largest of its kind—adds a new dimension to the kidney stone prevention literature, suggesting that adequately increasing hydration to prevent stone recurrence is likely more nuanced and patient-specific than previously understood.

The results were published in The Lancet.

Increasing fluid intake is a near-universal strategy for stone prevention

About 1 in 11 people in the United States develop a kidney stone, and nearly half experience recurrence or growth of an existing stone. Preventive therapy is tailored to the individual and may include increased fluid intake, dietary modification, pharmacologic therapy or even lifestyle changes such as weight loss, based on underlying risk factors and stone type.

Increasing fluid intake is almost always recommended as a key preventive measure for all patients with kidney stones, irrespective of stone type. However, adherence is a challenge, and likely contributes to the high rate of kidney stone recurrence.

Multicenter trial tests behavioral hydration program

A landmark study from the Urinary Stone Disease Research Network, coordinated by the Duke Clinical Research Institute, tested the effect of a multicomponent behavioral intervention program on kidney stone recurrence.

The PUSH study enrolled 1,658 adolescents and adults across six major U.S. academic sites, randomizing them to the control arm, which received the standard of care based on guidelines from the American Urological Association, or the intervention arm, which was assigned to a novel behavioral hydration program.

Both cohorts received Bluetooth-enabled “smart” water bottles to monitor and help with fluid intake. However, participants in the intervention arm also received personalized hydration goals, referred to as a “fluid prescription,” financial incentives, structured problem solving with a health coach, and other support.

Boosting fluid intake did not affect stone outcomes

The findings revealed that participants in the intervention cohort hydrated more than those in the control group, but this did not result in a significant difference in overall clinical endpoints.

“While there was no difference in stone events in the two groups over the two years, there was an improvement in urine output in both control and intervention groups, with the intervention group achieving a higher increase in urine output,” explains Sri Sivalingam, MD, a study coauthor and Director of the Center for Endourology and Stone Disease at Cleveland Clinic Hillcrest Hospital. Neither reached the guideline target of 2.5 liters of urine output per day.

Dr. Sivalingam points to jobs, lifestyles, and dietary preferences as a few examples of real-world challenges patients must contend with. Not to mention the potential difficulties associated with increased urine output, leading to worsening of pre-existing urinary symptoms such as urgency and frequency.

Reframing the conversation with patients

The authors conclude that the findings add an important dimension to patient counseling.

“If, despite all of our efforts, we still can't meet the desired endpoint, we need to reconsider how we counsel our patients,” Dr. Sivalingam says. “The expectations we set can be understandably frustrating and disappointing for patients,” he notes, adding that the ideal preventive strategy should be tailored and incorporate a range of patient-specific data points.

Emphasis on other modifiable factors

The study, he argues, highlights the need to focus equally on other factors, such as understanding barriers to adherence, while using a combination approach that includes hydration, dietary modifications and medical management.

Many specialists are already harnessing this shift in practice, but Dr. Sivalingam hopes the study will spark a broader reckoning about the limitations of achieving the target urine output for stone prevention.

A collaborative effort

The other centers participating in the trial included UT Southwestern Medical Center, Washington University, the University of Pennsylvania/Children’s Hospital of Philadelphia, the University of Washington and Mayo Clinic. The Urinary Stone Disease Research Network is funded by the National Institutes of Health and the National Institute of Diabetes and Digestive and Kidney Diseases.