Comparison of three different scoring systems in predicting success of retrograde intrarenal surgery in kidney stones larger than 20 millimeters.

Purpose: To evaluate stone free rate (SFR) predictivity of three different scoring systems in patients with kidney stones larger than 20 millimeters undergoing retrograde intrarenal surgery(RİRS).

Methods: Digital records of a total of 166 patients were reviewed retrospectively. Epidemiological characteristics (age, gender, medical history) of the patients, stone and affected kidney characteristics (size, volume, location, density, opaque, presence of urinary system anomaly, presence of stones in different calyx, number of stones, lower pole stone, renal infundibulopelvic angle (IPA), renal infundibulopelvic length (RIL), hydronephrosis), and operative characteristics (preoperative ureteral stent, operation duration, postoperative residual fragments, hospitalization time and complications were recorded. Each patient was scored separately according to the Resorlu-Unsal Scoring System (RUSS), the modified Seoul National University Renal Stone Complexity (S-ReSC) and R.I.R.S scoring systems based on the stone characteristics seen on CT.

Results: All three methods had statistically acceptable sensitivity and specificity values. Sensitivity for R.I.R.S nomogram is 62.3%, specificity is 77.1% (cut-off: 7.5 points, area under the curve (AUC):0.735, p < 0.001), sensitivity for RUSS nomogram is 60.7%, specificity is 77.9% (cut off: 2.5, AUC = 0.749, p < 0.001), sensitivity for the Modified S-ReSC nomogram was determined as 65.6% and specificity as 71.2% (cut off: 2.5, AUC = 0.743, p < 0.001). The residual stone ratio was found to be higher in the presence of lower pole stone. While the cut-off value for IPA was 44.5°, this value was calculated as 24.5 mm for RIL.

Conclusion: Three scoring systems demonstrate accceptable sensitivity and specificity in predicting stone free rate(SFR) with stones ≥ 20 mm. Multivariate analysis highlighted the superiority of the R.I.R.S. scoring system for SFR predictivity. In the presence of lower pole stones, IPA and RIL are important factors in predicting surgical success.