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PTU-55 Biliary stone characteristics determining difficulty at conventional ERCP and need for cholangioscopy-assisted lithotripsy

Introduction Stone clearance at ERCP is suboptimal, with NHS data suggesting 52% of ERCPs for stones are repeat procedures. Cholangioscopy-assisted lithotripsy is recommended for treating difficult bile duct stones (ESGE guidelines), but the characteristics of difficult stones are poorly defined, and patients may be undergoing conventional ERCP with limited chance of stone clearance. We sought to determine these characteristics and explore decision making in biliary endoscopy. Methods 53 biliary endoscopists independently assessed 20 cholangiograms with biliary stones (16 ERCPs, 4 MRCPs). Using Likert-type questionnaires each image was graded in 3 areas; ‘grading of stone difficulty’, ‘confidence of clearance with conventional ERCP methods’ and ‘likelihood of needing cholangioscopy-assisted lithotripsy’. Images were objectively assessed according to stone characteristics: ‘largest stone size’, ‘stone number’, ‘presence of stricture distal to stone’, ‘size of stone relative to distal duct size’. Univariate analyses were performed to determine the effect of these characteristics on endoscopists’ questionnaire responses. Results Largest stone size significantly affected endoscopists’ grading of difficulty, confidence of clearance with conventional ERCP methods and likelihood of needing cholangioscopy (p= <0.01 for all, Kruskal-Wallis (KW) test). As stone size increased, particularly >15 mm, endoscopists rated them as more difficult, were less confident with conventional methods and were more likely to need cholangioscopy. Presence of stricture distal to stone significantly affected responses to all 3 areas (p = <0.01 for all, c test), as did size of stone relative to distal duct (p= <0.01 for all, KW test). The presence of a stricture distal to a stone, and a larger stone relative to distal duct showed a clear trend in more difficult ratings, less confidence with conventional methods and a greater likelihood of requiring cholangioscopy. Stone number significantly affected responses to all 3 areas (p= <0.01 for all, KW test), however the presence of only one stone led to more difficult ratings, less confidence with conventional methods and an increased likelihood of using cholangioscopy. Conclusions Larger stone size, the presence of a stricture distal to a stone, a larger stone relative to the size of the distal duct and fewer stones result in endoscopists grading stones as more difficult and being more likely to use cholangioscopy. The result for stone number is unexpected and warrants further analysis. Our results suggest that pre-procedure stone characteristics may allow stratification of patients for advanced ERCP techniques. REFERENCE 1. Martin, H, et al|The national performance in the management of common bile duct stones in England. Gut 2021;70:A66.