Predictors of Stone Free Rate and Application of the Size, Topography, Obstruction, Number and Evaluation of Hounsfield Units (S.T.O.N.E) Scoring System in Predicting the Outcome in Patients Undergoing Semi-rigid Ureteroscopic Lithotripsy for Ureteric Calculi at a University Hospital of Nepal.

Background Ureteric colic is common urological emergency in patients with urinary stone disease. Semi rigid ureteroscopic lithotripsy is a widely acceptable treatment modality for ureteric calculi. Objective To evaluate the predicting factors of stone free rate (SFR) and application of the Size, Topography, Obstruction, Number and Evaluation of Hounsfield units (S.T.O.N.E) scoring system in predicting success rate of ureteroscopiclithotrisy (URSL) for ureteric calculi. Method This was a prospective hospital based observational study conducted at the Department of Surgery, Dhulikhel Hospital, Kathmandu University Hospital from October 2021 to September 2022. Patients undergoing ureteroscopiclithotripsy using laser and/or pneumatic lithotripsy for ureteric calculi were included in the study. Informed consent was taken from each patient and data collection was done by filling the proforma. Result A total of 82 patients were included in the study. Mean age of patients was 35.89 ± 11.51 years. Overall stone free rate was 80.5%. Stone free rate were 96.67% and 71.15% in moderate (6-9) and high (10-13) S.T.O.N.E score groups respectively. Stone size and S.T.N.O.E score were found to be significantly high in patients with retained stone following ureteroscopiclithotrisy (p value < 0.05). Duration of surgery was significantly high in high S.T.O.N.E score group (p< 0.05). However no significant correlation was found between patient characters like age, sex, Body mass index and Hounsfield units of stone with stone free rate in this study. The area under the curve of the receiver operating characteristic curve for the S.T.O.N.E score and stone size were 0.693 and 0.660 respectively in this study. Conclusion Stone size and S.T.O.N.E score can be used as predictors of success following semirigid ureteroscopic lithotripsy. The value of S.T.N.O.E score has good predictive value for SFR and duration of surgery. There was no significant impact of patient's age, sex, Body mass index and Hounsfield units of stone in stone free rate following ureteroscopic lithotrisyin this study.