Outcomes and rates of dissolution therapy for uric acid stones

Introduction: To describe the outcomes and quantify the rate of uric acid stone medical dissolution therapy using automated, software-generated stone volume measurements. Methods: A sample of patients treated with oral dissolution therapy was reviewed from a single institution between 2008 and 2019. Baseline patient demographics, metabolic urine testing and stone characteristics were collected. Computed tomography (CT) scan images were evaluated using the quantitative Stone Analysis Software (qSAS) to obtain total stone volume (TSV), maximum diameter (MD) and stone number. Rate of dissolution using total stone volume was calculated over the treatment period. Results: Twenty-seven patients were started on oral dissolution therapy, corrected for renal function. After mean duration of 180 days (range 41–531), 16 patients failed treatment resulting in surgical therapy. Twenty stones in 11 patients showed complete or partial dissolution. Compared to those who failed treatment, patients with complete or partial dissolution had lower 24 h urinary uric acid and higher treatment urine pH. Thirteen (65%) stones showed complete dissolution after a mean 167.6 days. Rate of change for responders was 4.73 mm³ or 0.6% of total stone volume per day. Time to dissolution of one half of stone volume based on total stone volume was 86 days (12.30 weeks). Discussion/conclusions: Software-calculated total stone volume may be an effective method of measuring uric acid stone response to oral alkalization therapy. Stone volume decreased by 50% after 12.3 weeks of treatment and could be an important benchmark for oral dissolution therapyoral dissolution therapy. Further studies with a larger sample and validation of the software are needed to confirm if this can be used to guide surveillance schedules for dissolution therapy.