The survival of flexible ureterorenoscopes in terms of the total stone area and total usage time

Abstract

Introduction: We investigated the survival of a flexible ureterorenoscope (FURS) in regard to the total stone area (TSA) and total usage time (TUT) to determine the cutoff values for its survival.

Materials and Methods: Data were obtained from 1326 patients who underwent flexible ureterorenoscopy. The stone area and the usage time of the FURS were obtained in each case. The data from each FURS were considered as a group. The TSA was calculated as the sum of the stones for which only one FURS broke, and the TUT was calculated as the sum of the time of use within the body in all cases during the tool's survival. Data from 13 groups of 1258 patients were analyzed in regard to the TSA and TUT.

Results: We found a positive correlation of the case number with the TSA and TUT. The Pearson correlation coefficients were 0.983 and 0.937 for the TSA and TUT, respectively (p < 0.05). The mean case number, TSA, and TUT where only one FURS was used were 97.38 +/- 31.34, 11,886 +/- 4567.93 mm(2), and 5160 +/- 1570.52 minutes, respectively. The area under the curve (AUC) of the receiver operating characteristic curve of the FURS survival for the TSA was 91.7% (95% confidence interval [CI]: 0.76-1.07). The best cutoff value for the FURS survival was 6838 mm(2), with a sensitivity of 91%. The results for the AUC and the best cutoff value in regard to the TUT for using only one FURS were 66.7% (95% CI: 0.4-0.93) and 4617 minutes, respectively, with a sensitivity of 66%. If the cutoff value is taken as the average value of the TSA and TUT, the sensitivity rate drops to similar to 58% and 50%, respectively.

Conclusion: FURS can be safely used when the stone area and TUT are about 9158 mm(2) and 4617 minutes, respectively, with a sensitivity of 66%.