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Background: Stone nomogram by Micali et al., able topredict treatment failure of shock-wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PNL) in the management of single 1-2 cm renal stones, was developed on 2605 patients and showed a high predictive accuracy, with an area under ROC curve of 0.793 at internal validation. The aim of the present study is to externally validate the model to assess whether it displayed a satisfactory predictive performance if applied to different populations., Methods: External validation was retrospectively performed on 3025 patients who underwent an active stone treatment from December 2010 to June 2021 in 26 centers from four countries (Italy, USA, Spain, Argentina). Collected variables included: age, gender, previous renal surgery, preoperative urine culture, hydronephrosis, stone side, site, density, skin-to-stone distance. Treatment failure was the defined outcome (residual fragments >4 mm at three months CT-scan)., Results: Model discrimination in external validation datasets showed an area under ROC curve of 0.66 (95% 0.59-0.68) with adequate calibration. The retrospective fashion of the study and the lack of generalizability of the tool towards populations from Asia, Africa or Oceania represent limitations of the current analysis., Conclusions: According to the current findings, Micali's nomogram can be used for treatment prediction after SWL, RIRS and PNL; however, a lower discrimination performance than the one at internal validation should be acknowledged, reflecting geographical, temporal and domain limitation of external validation studies. Further prospective evaluation is required to refine and improve the nomogram findings and to validate its clinical value.

Introduction: Ureteral access sheath (UAS) is widely used in flexible ureteroscopy and laser lithotripsy (FURS) based on better stone-free rates, lower intrarenal pressure and fewer complications. However, it also rises surgical costs and may injure the ureteral wall. The main objective of our study is to compare safety and efficacy of FURS with and without UAS to evaluate whether its use is justified in all cases., Materials and Methods: We performed a retrospective observational analytic study based on a prospective database. A total of 241 consecutive patients who underwent FURS for upper ureter and renal stones between January 2018 and May 2020 were included for analysis and divided into two groups upon UAS use. We compared demographic data, stone characteristics, prestenting, operative time, need for ureteral stent, postoperative urinary tract infection, renal colic and need for ancillary procedures., Results: A total of 198 patients (82.2%) were included in the group without UAS. Operative time was significantly shorter in the group of patients without UAS than those with UAS (64.6 minutes ± 29.5 vs. 89.9 minutes ± 2.8 respectively; p 0.010). Both groups had similar rates of colic pain and urinary tract infection. Ancillary procedures were more frequent in the UAS group (37.2 vs. 21.2%; p 0.026), but significance was lost in multivariate assessment., Conclusion: FURS without UAS seems to be as safe as FURS with UAS but requires less ancillary procedures. An additional advantage is shorter operative time., (Copyright © 2021. Published by Elsevier España, S.L.U.)