Feasibility and Safety of a Novel Pig-tail Inside Stent for Unresectable Malignant Hilar Biliary Obstruction: A Single-center Case Series (With Video).

Background and Aims: Inside stents are increasingly used for malignant hilar biliary obstruction because of their prolonged patency and removability. Although reported migration rates vary, migration remains a clinical concern, and deployment in angulated bile ducts can be technically challenging. We evaluated a novel pig-tail type inside stent (X-FLEX ARC type) in unresectable malignant hilar biliary obstruction. Methods: This retrospective single-center case series included consecutive patients who underwent X-FLEX ARC type placement between October 2024 and December 2025. Procedural characteristics were evaluated for the 26 deployed ARC-type stents, whereas clinical outcomes were evaluated after the 13 initial drainage procedures. Results: Eighteen patients underwent 21 endoscopic retrograde cholangiopancreatography sessions, during which 26 ARC-type stents were deployed. Deployment into the intended bile duct branch was completed in all selected sessions. The median placement time was 4.0 min, and additional maneuvers were required for five stents (19.2%). Among 13 initial drainage procedures, clinical success was achieved in 11 (84.6%), and no procedure-related adverse events occurred. Recurrent biliary obstruction (RBO) occurred after five procedures (38.5%), with a median time to RBO of 167 days (95% confidence interval, 137-not reached). No ARC-type stent migration was observed. Conclusions: This preliminary case series provides descriptive information on ARC-type inside stent placement and removability in selected patients with unresectable malignant hilar biliary obstruction. Prospective comparative studies are needed to determine its technical applicability and effects on stent migration and long-term patency.