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

Authors Sirirak N, Sangkum P, Phengsalae Y, Kongchareonsombat W, Leenanupunth C, Ratanapornsompong W, Ketsuwan C

Received 28 January 2021

Accepted for publication 8 March 2021

Published 23 March 2021 Volume 2021:13 Pages 147—154


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 3

Editor who approved publication: Dr Jan Colli

Noppavut Sirirak, Premsant Sangkum, Yada Phengsalae, Wisoot Kongchareonsombat, Charoen Leenanupunth, Wattanachai Ratanapornsompong, Chinnakhet Ketsuwan

Division of Urology, Department of Surgery, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, 10400, Thailand

Correspondence: Chinnakhet Ketsuwan Tel +66-2-2011536
Fax +66-2-2794704
Email [email protected]

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 (p = 0.002) and stone size (p = 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 (r = 0.22, p = 0.006; r = 0.30, p < 0.001; and r = 0.27, p < 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.

Keywords: ureteroscopy, S.T.O.N.E. score, stone-free rate

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