External validation of the T.O.HO. score as predictor of success after retrograde intrarenal surgery

BACKGROUND: To assess the effectiveness of T.O.HO. (Tallness, Occupied lesion, Houndsfield unit evaluation) score in predicting the retrograde intrarenal surgery (RIRS) success and to validate this scoring system. METHODS: The age, sex, previous stone surgery, hospitalization, surgery duration, postoperative complication, stone length, stone location, stone density, stone number, lateralization, presence of hydronephrosis, and presence of preoperative stent datas of 611 patients who underwent RIRS in our clinic between January 2013 and January 2021 were retrospectively assessed. The patients were divided into two groups as successful and unsuccessful. The T.O.HO scores of all patients were calculated. RESULTS: The success rate was 72.5%. Compared to the unsuccessful group, stone length and stone density were lower, surgery duration was shorter and there were less lower pole stones in the successful group (p < 0.001). No significant difference was found between the two groups in terms of the other parameters. The T.O.HO. score was significantly lower in the successful group compared to the unsuccessful group (p < 0.001). According to the multivariate logistic regression analysis, stone length (OR: 0.905; 95% Cl: 0.866–0.946; p < 0.001), lower pole location (OR: 0.546; 95% Cl: 0.013–0.296; p < 0.001), stone density (OR: 0.999; 95% Cl: 0.998–1; p = 0.044) and the T.O.HO. score (OR: 0.684; 95%Cl: 0.554–0.844; p < 0.001) were found as the independent risk factors for RIRS success. ROC curve analysis showed that the T.O.HO. score could predict the RIRS success with 7.5 cut-off point (AUC: 0.799, CI: 0.76–0.839; p < 0.001). CONCLUSION: The T.O.HO. score can predict RIRS success with a high rate of accuracy.