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Background: The aim of this study was (1) to explore effect of ureteral access sheath (UAS) use on primary retrograde intrarenal surgery (RIRS) outcomes, short-term kidney functions, radiation exposure, and ureteroscope lifetime (URS-LT) and (2) to reveal factors that predict UAS insertion failure. Materials and Methods: Patients ( n  = 1318) who underwent RIRS without UAS (Group 1), those who had operation with a <11-13 Fr (Group 2), and those with a ≥11-13 Fr UAS were matched (1:1:2) and compared. Stone-free rate (SFR), intra- and postoperative complications, acute kidney injury (AKI), fluoroscopy time, URS-LT, and UAS insertion failure were the outcomes. Results: SFR, which was highest in Group 3 (75%, 71% and 87.3%, respectively; P  = .001), was significantly associated with use of ≥11-13 Fr (odds ratio [OR]: 4.2, P  < .001), but was not with use of <11-13 Fr UAS (OR: 1.3, P  = .3). Group 3 had less need for auxiliary procedure (15%, 16%, and 7.4%, respectively; P  = .03). Five percent of patients had a risk of AKI, but only 0.3% developed AKI. Although UAS use was protective against creatinine increase (OR: 0.65, P  = .02), increased risk of AKI was only associated with female gender (OR: 5.5, P  < .001). Fluroscopy times were 5, 15, and 87 sn, respectively ( P  < .001). Short URS-LT was strongly associated with high frequency of lower calix stones ( r  = -0.94, P  = .005), but URS-LT was not correlated with sheathless case rate ( r  = 0.59, P  = .22). UAS insertion success in first attempt was more likely in younger (OR: 0.99, P  = .03), hydronephrotic (OR: 3.4, P  < .001), and female cases (OR: 1.5, P  = .008). But absolute UAS insertion failure was associated with female gender (OR: 2.7, P  = .017). Conclusions: Not any UAS use but a higher caliber UAS use may improve SFR and protect against AKI after RIRS. Although UAS insertion failure is seen mostly in men, it may be more challenging in women owing to less efficacy of preoperative Double-J stent.

Objectives: To complement our previous findings regarding effect of ureteral access sheath (UAS) use, we checked RIRSearch database for patients who operated without using UAS. The aim of the study was to understand these new data better by comparing outcomes of retrograde intrarenal surgery (RIRS) that continued sheathless after a failed UAS insertion vs those planned and completed sheathless. Materials and Methods: Data of 195 patients who underwent sheathless RIRS for kidney and/or ureteral stones between 2011 and 2021 were retrieved from the database. Patients divided into two groups: cases who were planned and completed sheathless ( n  = 110, Group 1) and those who proceeded without UAS after insertion failure ( n  = 85, Group 2). After propensity score matching (PSM), each group consisted of 76 patients. Results: After PSM, stone-free rate for Group 1 (90.8%) was significantly higher than stone-free rate of Group 2 (76.3%) in sheathless RIRS ( p  = 0.02). Also postoperative complication rate was significantly lower in Group 1 (10.5%) than in Group 2 (27.6%) ( p  = 0.007). In Group 2, median operating time was longer (60 minutes, interquartile range [IQR]: 40-80) and more unplanned auxilliary procedure (22.4%) was needed than Group 1 (45 minutes, IQR: 40-50 and 3.9%) (both p  = 0.001). Stone burden (odds ratio [OR]: 1.002, p  = 0.019) and stone density (OR: 1.002, p  = 0.003) were associated with high risk of residual stones after RIRS. Higher hydronephrosis grades were associated with increased stone-free rates (OR: 0.588 for residual stone risk, p  = 0.024). Cases who completed sheathless by dusting all available stones, as planned preoperatively, were more likely to have stone-free status after RIRS than those who proceeded sheathless after UAS insertion failure (OR: 2.645, p  = 0.024). Conclusions: Operation course after UAS insertion failure may be more challenging. In cases who performed without using UAS, surgeons who proceed with procedure sheathless after UAS insertion failure may more frequently run into complications and may fail achieving stone-free status compared with sheathless-planned cases.

Introduction: The Modified Seoul National University Renal Stone Complexity Score (S-ReSC) is a simple model based solely on stone location regardless of stone burden. The aims of this study were to validate S-ReSC for outcomes and complications of retrograde intrarenal surgery (RIRS) and to evaluate its predictive power against the stone burden., Material and Methods: Data of 1007 patients with kidney stones who had undergone RIRS were collected from our RIRSearch database. Linear-by-linear association, logistic regression, ANOVA/post hoc analysis and ROC curve (with Hanley and McNeil's test) were used for evaluation. The main outcomes were stone-free status and complications of RIRS., Results: The overall stone-free rate was 76.8% (773/1007). Higher S-ReSC scores were related to lower stone-free rates and higher total, perioperative and postoperative complication rates ( p <.001, p <.001, p =.008 and p <.001, respectively). S-ReSC score ( p =.02) and stone burden ( p <.001) were independent predictors of stone-free status. But stone burden (AUC = 0.718) had a more powerful discriminating ability than the S-ReSC score (AUC = 0.618)., Conclusions: The S-ReSC score is able to predict not only stone-free status but also complications of RIRS. Although this location-only based scoring system has a fair discriminative ability, stone burden is a more powerful predictor of stone-free status after RIRS. An ideal scoring system aiming to predict outcomes of RIRS must include stone burden as a parameter.