The following article features coverage from the American Urological Association (AUA) 2019 meeting. Click here to read more of Renal & Urology News’ conference coverage.

CHICAGO—Urinary metabolic abnormalities, and possibly obstruction, explain the formation of bladder stones made from uric acid, investigators reported at the 2019 American Urological Association annual meeting.

Julio Chong, MD, and colleagues from Icahn School of Medicine at Mount Sinai in New York, evaluated 66 patients who underwent bladder stone procedures. Of these, 27 formed uric acid bladder stones and received medical management, including 12 recurrent formers and 15 who never re-formed stones.

Results showed that significantly more recurrent formers had bladder stones composed of uric acid: 63.2% vs 31.9% of never re-formers. Flow rate, prostate size, and serum uric acid did not differ between groups and thus could not explain recurrence. Rather, recurrent formers of uric acid bladder stones had significantly higher post void residual volume: 127 vs 29 mL. They were also significantly less compliant with urinary alkalization therapy: 33% vs 79%. Recurrent uric acid stone formers produced less urine (1.4 vs 1.7 L) and had more acidic urine (pH 5.3 vs 5.4). Recurrent uric acid stone formers had significantly higher uric acid supersaturation: 2.67 vs 1.46 DG. They also displayed higher 24-hour urinary citrate (814.6 vs 415.7 mg) perhaps due to citrate supplementation for their 24-hour urine tests.

“Uric acid bladder stones can be an indication of severe urinary metabolic derangements,” Dr Chong told Renal & Urology News. “Patients with the diagnosis of uric acid bladder stones should have complete 24-hour urine studies to determine risk factors to mitigate and reduce risk of recurrent bladder stones. Urinary alkalization and reducing post-void residuals can be helpful in preventing future uric acid bladder stones.”


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Reference

Chong J, Brown C, Katims A, et al. Uric acid supersaturation and elevated post void residuals are driving forces for uric acid bladder stone pathogenesis and is mitigated by compliance to urinary alkalinization. Presented at the 2019 American Urological Association annual meeting held May 3-6 in Chicago. Abstract MP12-12.