Endoscopic Appearance After Transpancreatic Precut Sphincterotomy: Classification and Implications for Biliary...

Background/Objectives: Biliary cannulation remains a major challenge during endoscopic retrograde cholangiopancreatography (ERCP). Transpancreatic precut sphincterotomy (TPS) is an effective rescue technique, yet its technical endpoints and optimal post-TPS cannulation strategies have not been standardized. We aimed to establish a practical cannulation strategy based on post-TPS endoscopic appearance. Methods: We retrospectively analyzed 135 patients who underwent TPS for difficult biliary cannulation between 2008 and 2026. Endoscopic images and videos obtained before and after TPS were reviewed. Post-TPS appearance was evaluated by focusing on the bile duct structure and incised red epithelial surface, and clinical outcomes, adverse events, and predictors of successful biliary cannulation were assessed. Results: Post-TPS endoscopic appearances were classified into four patterns. A hypothesis-generating interpretation was performed to link these patterns to three previously described types of distal pancreaticobiliary anatomies-short common channel, long common channel, and separate orifices. Specifically, (1) a white duct-like structure outside the incised red epithelial surface indicated a short common channel; (2) a hole-like structure within the incised red epithelial surface and (3) the absence of any identifiable ductal structure indicated a long common channel; and (4) preservation of an alternative orifice was considered indicative of separate orifices. Selective biliary cannulation during the same session was successful in 74.1% of patients (overall success rate, 88.1%). Post-ERCP pancreatitis occurred in 12.6% of patients, and bleeding occurred in two cases. Procedures performed predominantly by non-experts showed higher initial success rates without increased adverse events compared with those performed by experts. Exploratory multivariable analyses revealed that adequate incision was the only significant predictor of successful biliary cannulation. Conclusions: Post-TPS endoscopic appearance may suggest the distal pancreaticobiliary anatomy and provide practical guidance for directing biliary cannulation.