Mp12-12 uric Acid Supersaturation and Elevated Post Void Residuals Are Driving Forces for Uric Acid Bladder Stone Pathogenesis and Is Mitigated by Compliance to Urinary Alkalization

Abstract

INTRODUCTION AND OBJECTIVES: Uric acid bladder stones can be indicative of severe metabolic abnormalities. Men may be at increased risk for uric acid bladder stone recurrence secondary to obstruction and urinary metabolic derangements. The objective of this study is to evaluate for clinical and metabolic factors in the pathogenesis and prevention of recurrent uric acid bladder stones.METHODS: A database of patients who underwent bladder stone procedures from 2012 to 2018 (n[66) was analyzed to identify patients who formed uric acid bladder stones (n[27). Clinical features, metabolic abnormalities, and compliance to urinary alkalization were assessed between individuals who never reformed uric acid bladder stones (n[15) vs. those forming recurrent stones (n[12) despite medical management.RESULTS: Bladder stones are more likely to be uric acid in composition in men who form recurrent stones (12/19, 63.2%) compared to those who do not (15/47, 31.9%) (p[0.0195). There were no differences in flow rate, prostatic size, or serum uric acid between groups. Patients forming recurrent uric acid bladder stones have a higher post void residual (PVR) (127 vs 29 cc, p[0.035). In the non-recurrent group, 79% (11/14) were compliant with urinary alkalization vs. 33% (4/12) in the recurrent group (p[0.0199). Recurrent uric acid stone formers generally had lower urinary volume and urinary pH (1.4 vs 1.7L and 5.3 vs 5.4, not statistically significant). Recurrent uric acid stone formers had higher uric acid supersaturation (SSUA) (2.67 vs. 1.46, p [ 0.005) and higher 24-hour urinary citrate (814.6 vs 415.7 mg, p[0.0146) compared to non-recurrent uric acid bladder stone formers (Table 1).CONCLUSIONS: Uric acid bladder stone formation is largely influenced by urinary metabolic abnormalities. Obstruction and urinary stasis may play a role in its pathogenesis. Recurrent uric acid bladder stone formers have increased urinary uric acid supersaturation and increased PVR, which may be driving forces for stone recurrence. Urinary citrate levels were higher in recurrent stone formers, but patients may be taking citrate supplements for their 24-hour urine tests. Long-term compliance to urinary alkalization is associated with successful prevention of recurrent uric acid urolithiasis.