Ureteral stent encrustation: evaluation of available scores as predictors of a complex surgery

Background: Stent Encrustation is an uncommon event (13%) with a significant impact in patients' management. Aim of our study was to evaluate the available grading systems for encrusted stents. Methods: A retrospective analysis of encrusted stents was performed in four Italian centers between 2006 and 2020. Encrusted stents were classified according to four classifications: the Forgotten Encrusted Calcificated (FECal) score, the Kidney Ureter Bladder (KUB) score, the Visual Grading for Ureteral Encrusted Stent Classification and the Encrustation Burden Score (EBS). Classifications were evaluated to predict complex surgery defined as: long operative time (>60min); need of more than one surgery; need of a percutaneous approach. The scores were compared with Receiver Operating Characteristic (ROC) analysis as predictors of complex surgery. Results: 77 patients were evaluated with a median age of 62 years (65/70). Overall FECal score >2 was present in 45/77 (58%) patients, median KUB score was 9 (6/14) and severe EBS was found in 47/77 (63%) patients. Patients were managed with cystolithotripsy in 13/77 (17%), with ureteroscopy in 58/77 (75%) and with Percutaneous Nephrolithotomy (PCNL) in 6/77 (8%). Overall, 6/77 (8%) patients required a second intervention to remove the encrusted stent. All classifications predicted the need of complex surgery. On ROC analysis KUB score presented a better accuracy in predicting complex surgery compared to FECal, V-GUES and encrusted burden. Conclusions: KUB score, FECal score, V-GUES score and encrustation burden accurately predict the need of a complex surgery. KUB showed to be superior to other classifications according to our results.