IP63-08 CHARACTERIZATION AND PREDICTION OF STONE ACTIVITY AMONGST BRUSHITE STONE FORMERS USING 24-HOUR URINE PARAMETERS

Ryan L. Steinberg; Kyle Berst; Cheney Hurley; Melissa Swee; Timothy Chow; Chad R. Tracy

doi:10.1097/01.JU.0001191660.34244.02.08

INTRODUCTION AND OBJECTIVES: Brushite (calcium monohydrogen phosphate) stone formers have high rates of stone recurrence. Yet, most labs do not report the supersaturation of brushite, rather only for calcium phosphate in general. We sought to characterize the 24-hour urine chemistry of brushite stones formers with and without stone activity, as well as perform a sensitivity analysis of supersaturation of calcium phosphate (SSCaPhos) in predicting stone activity. METHODS: A database of all brushite stone formers at our institution from 1/2014 to 6/2024 was queried. All 24-hour urine studies (24U) were labeled with regards to stone activity. Stone activity was defined as new stone formation, growth of an existing stone, stone pain, or passage of/treatment for a stone not previously detected. Wilcoxon rank-sum analysis was used to compare 24-hour parameters (p<0.05). A generalized linear mixed model with a logit link and spline term for SSCaPhos was generated to examine the association between SSCaPhos and stone activity with adjustment for family history, body mass index (BMI), prior stone episodes, and anti-lithogenic medication use. The model included a random intercept for each participant to account for repeated urine collections. RESULTS: 69 patients completed a total of 195 24Us, of which 106 (54%) were associated with stone activity. 24Us without stone activity revealed significantly lower urinary calcium (199 vs 246, p=0.01), magnesium (96 vs 109, p=0.01), and SSCaPhos (1.80 vs 2.29, p=0.01). SSCaPhos showed a significant overall association with stone activity (p=0.038). The probability of stone activity increased sharply as SSCaPhos increased from 1.0 to 2.5, then plateaued at higher levels of SSCaPhos (Figure 1). More specifically, the odds of stone activity were 1.98 times higher when SSCaPhos = 2.5 compared to 1.5, after adjusting for covariates. CONCLUSIONS: SSCaPhos appears to be a reasonable predictor for stone activity among brushite stone formers. 24U in those with stone activity show significantly higher levels of urinary calcium and SSCaPhos, but no difference in pH or citrate. Strategies to aggressively minimize SSCaPhos, especially through manipulation of urinary calcium, appear to be key to stopping stone activity.

IP63-08 CHARACTERIZATION AND PREDICTION OF STONE ACTIVITY AMONGST BRUSHITE STONE FORMERS USING 24-HOUR URINE PARAMETERS

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