Introduction
In parallel to minimal invasive surgery trend in urological surgery,
flexible ureterorenoscopy (f-URS) and laser lithotripsy gained a
significant popularity in the treatment of renal stones. Despite the
technological advancements in optical and lithotripsy systems there are
still some limiting factors including stone burden and abnormal renal
anatomy [1]. To standardize reporting the outcomes in scientific
studies and pre-operative counseling of patients some scoring systems
were developed but none of them gained popularity and were not widely
used. The ideal nomogram should include all the variables that might
affect the outcome, besides should be simple, accurate and easy to apply
in office conditions. The success of a f-URS can not only be evaluated
with stone-free rates, but the ideal success should be stone-free rates
without any complication or with acceptable complication rates. So, the
ideal scoring system should predict the complications besides the stone
free-rates. The first scoring system for predicting success of f-URS was
developed by Resorlu et al. in 2012 [2].After than modified Seoul
National University Stone Complexity score (S-ReSC) [3], a nomogram
by Ito et al. [4] and R.I.R.S. scoring system [5] were
developed. We aimed to externally validate and compare these four
scoring systems for predicting capabilities of both the stone-free
status and complications in a multi-institutional study.