Hospital volume in ureterorenoscopic stone treatment: 99 operations per year could increase the chance of a better outcome-results of the German prospective multicentre BUSTER project.

Background: Despite the high utilisation of ureterorenoscopy (URS) in interventional stone treatment, there is little evidence of any link between annual hospital volume and outcome.

Methods: From January to April 2015, data from 307 URS patients were prospectively recorded in the multicentre observational BUSTER-Trial (Benchmarks of ureterorenoscopic stone treatment-results in terms of complications, quality of life, and stone-free rates). The best threshold value for annual hospital volume with an independent effect on the outcome (measured on stone-free and complication rates) of our study group was established with logistic regression.

Results: In 38.4% of cases of renal and 61.6% of ureteral stones, median stone size was 6 mm with an interquartile range (IQR) of 4-8 mm. The annual URS rate in the 14 participating hospitals ranged from 77 to 333 (median 144; IQR 109-208). The binary endpoint as a combination of completely stone-free or residual fragments small enough to pass spontaneously and a maximum complication severity of Clavien-Dindo grade 1 was attained in 234/252 (92.9%) cases with a hospital volume of ≥ 99 URS compared with 43/55 (78.2%) in < 99 URS (p = 0.002). Adjusted for patient-, stone- and physician-related factors, an annual hospital URS volume of ≥ 99 increases the chance of an optimum outcome (OR = 3.92; 95% CI 1.46-10.51; p = 0.007).

Conclusions: An independent effect of URS hospital volume on outcome quality in the 14 participating hospitals was demonstrated. Threshold values for annual case numbers should be scientifically established irrespective of the considered procedure.