External validation of six scoring systems for predicting retrograde intrarenal surgery outcomes in obese patients

To determine which scoring systems are most effective in predicting stone-free rates after retrograde intrarenal surgery in our own obese patient group and the factors that may influence this rate.

a total of 251 patients were included in the study. Patients were divided into two groups, stone-free and nonstone-free, on the basis of the presence of residual stones. Patient characteristics such as age, sex, body mass index, e-GFR, and stone laterality were recorded. The characteristics of the stone and the operated kidney included stone diameter, laterality, volume, location, opacity, hounsfield unit, operative time, multiple stones, the presence of multiple calyceal stones, the infundibulopelvic angle, and the renal infundibular length.

210 patients (83.7%) were stone free postoperatively, whereas 41 patients (16.3%) had residual fragments. patients with residual stones had significantly larger median stone diameters (20 mm vs. 13 mm, p < 0.001) and greater stone volumes (1560 mm³ vs. 758 mm³, p < 0.001). Multiple stones (60% vs. 19.4%, p < 0.001) and multiple calyceal involvement (57.5% vs. 16.6%, p < 0.001) were also more frequently observed in patients with residual fragments. All five stone scoring systems, R.I.R.S., RUSS, ITO, STONE and T.O.HO presented significantly higher median scores in the residual group than in the stone-free group. TOHO score exhibited the strongest discriminatory performance.

All scoring systems except the modified S-ReSC system were found to be effective in predicting the SFR, with stone diameter, multiple stones, and TOHO scoring system playing a leading role in this predictive accuracy.