External validation and comparison of current scoring systems in
retrograde intrarenal surgery: multi-institutional study with 949
Objectives: To externally validate and compare Resorlu-Unsal stone
score(RUSS), modified Seoul National University Renal Stone Complexity
Score(S-ReSC), Ito’s nomogram and R.I.R.S. scoring systems for
predicting capabilities of both the stone-free status and complications
in a multi-institutional study. Materials and Methods: We performed a
retrospective analysis of 949 patients who were underwent flexible
ureterorenoscopy (f-URS) and laser lithotripsy for renal stones in two
institutions between March-2015 and June-2020. The RUSS, modified
S-ReSC, Ito’s nomogram and R.I.R.S. scores were calculated for each
patient by same surgeon on imaging methods. Results were compared for
their predictive capability of stone-free status and complications.
Results: Of 949 patients 603 were male and 346 were female with a mean
age of 47.2±14.3 (range 2-84years). Mean stone burden was 102.6±42.2
(48-270mm2). All nomograms predicted stone-free status (AUC were 0.689,
0.657, 0.303 and 0.690, respectively). All four scoring systems
predicted complications with AUC values of 0.689, 0.646, 0.286 and 0.664
for RUSS, modified S-ReSC, Ito’s nomogram, R.I.R.S., respectively.
Although all scoring systems were able to predict complications only
Ito’s nomogram was able to predict Clavien ≥2 complications. Conclusion:
All four scoring systems (RUSS, modified S-ReSC, Ito’s nomogram and
R.I.R.S.) could predict stone-free status after f-URS, however the AUC
values are not satisfactory in our large patient cohort. Although these
scoring systems were not developed for predicting post-operative
complications, they were associated with complications in our study.
However, these four scoring systems have some significant limitations.
The ideal scoring system is yet to be developed.