External Validation of the S.T.O.N.E. Score in Predicting Stone-Free Status After Rigid Ureteroscopic Lithotripsy.

BACKGROUND

The Size, Topography, Obstruction, Number, and Evaluation of Hounsfield units (S.T.O.N.E.) scoring system has been proposed as a novel prognostic surgical classification for urolithiasis in predicting success rate and complications.

OBJECTIVE

We carried out an externally validated S.T.O.N.E. score on rigid ureteroscopic lithotripsy (rURS).

MATERIALS AND METHODS

The data of patients who had undergone rURS between 2012 and 2019 at a tertiary referral center were audited retrospectively. The S.T.O.N.E. score was calculated based on factors determined through preoperative computed tomography images and was analyzed in association with stone-free rate (SFR), operating time, surgical complications, and length of stay (LOS).

RESULTS

A total of 155 patients were included in the study with a median stone size of 10 mm (7-12) and a median S.T.O.N.E. score of 9 (8-10). The overall SFR was 89.68%. SFRs were 100.0%, 97.83%, and 77.42% in low (5), moderate (6-9), and high (10-13) score groups, respectively. The S.T.O.N.E. score ( = 0.002) and stone size ( = 0.037) were predictive factors for SFR in multivariate analysis. Moreover, there was a significant correlation between the S.T.O.N.E. score and operative time, LOS, and presence of complications ( = 0.22, = 0.006; = 0.30, < 0.001; and = 0.27, < 0.001, respectively). The area under the curve of the receiving operator characteristics' curve for the S.T.O.N.E. score was 0.815.

CONCLUSION

The S.T.O.N.E. scoring system is simple and effective in predicting postoperative outcomes; therefore, this score would be a valuable tool in clinical planning for every patient who undergoes rURS.