Jonathan Harper, MD, shares PUSH trial findings on hydration and stone recurrence

In an interview at the 2026 American Urological Association Annual Meeting, Jonathan D. Harper, MD, discussed findings from a secondary analysis of the PUSH randomized controlled trial, highlighting how modest increases in urine output and the potential use of urine osmolality may help refine hydration recommendations for kidney stone prevention.¹ Harper is a professor of urology at the University of Washington in Seattle.

The original PUSH trial was designed to address a longstanding challenge in stone prevention: achieving the guideline-recommended urine volume target of 2.5 L/day. Harper explained that many patients struggle to consume enough fluid to reach this goal, prompting investigators to test whether a behavioral intervention could improve fluid intake and urine output compared with standard guideline-based counseling. Although participants in the intervention arm successfully increased their 24-hour urine volume, the trial did not demonstrate a reduction in symptomatic stone events.

Related: Behavioral hydration program falls short in reducing kidney stone recurrence

As part of a secondary analysis of this trial, investigators assessed data from 1461 adult participants enrolled in the PUSH trial to examine the relationship between changes in urine volume, urine osmolality, and stone recurrence. The median change in urine volume from baseline was an increase of 438 mL/day—approximately 15 oz. Further, patients who increased their urine volume by greater than this median experienced fewer recurrent stone events, even when they did not reach the guideline target of 2.5 L/day. After adjustment for demographic and clinical factors, these patients had a 24% lower likelihood of symptomatic or radiographic stone recurrence compared with those whose urine volume increased less (OR, 0.76; 95% CI, 0.59 to 0.98; P = .04). Harper emphasized that this finding suggests clinically meaningful benefits may be achieved through more modest increases in hydration, rather than requiring all patients to attain the traditional urine output goal. Additionally, patients who maintained higher urine volumes from baseline through follow-up experienced significantly lower risks of both symptomatic stone recurrence (multivariable adjusted HR, 0.51; 95% CI, 0.31 to 0.83; P < .01) and less symptomatic and/or radiographic recurrence (adjusted OR, 0.67; 95% CI, 0.51 to 0.87; P < .01).

A second key finding involved urine osmolality, a measure not routinely incorporated into most stone prevention practices. Harper noted that lower urine osmolality demonstrated a clear dose-response relationship with symptomatic stone recurrence, with lower quintiles of osmolality associated with fewer stone events (P = .04). In contrast, achieved urine volume alone did not show the same significant relationship across volume quintiles (P = .12). These results suggest that urine osmolality may provide important context beyond urine volume when assessing hydration status and recurrence risk. According to Harper, incorporating urine osmolality alongside traditional 24-hour urine measurements may help guide fluid intake recommendations for stone prevention.

REFERENCE

1. Harper J, Lieske J, Desai A, et al. Urine volume and urine osmolality and risk of recurrent stone events: results from the prevention of urinary stones with hydration (PUSH) trial. J Urol. 2026;215(5S2):e6. doi:10.1097/01.JU.0001192572.07890.f8.13