Endoscopic Ultrasound-Guided Gallbladder Drainage for Malignant Distal Biliary Obstruction: Current Evidence, Technical Considerations, and Future Directions.

Malignant distal biliary obstruction (MDBO) is most commonly managed by endoscopic retrograde cholangiopancreatography (ERCP) with self-expandable metal stent placement. When ERCP fails or is not feasible, endoscopic ultrasound-guided biliary drainage (EUS-BD) has increasingly replaced percutaneous transhepatic biliary drainage in expert centers. Endoscopic ultrasound-guided gallbladder drainage (EUS-GBD) has emerged as an indirect route for biliary decompression when the cystic duct is patent. This comprehensive narrative review focuses on the anatomical rationale, patient selection, procedural technique, comparative positioning, clinical outcomes, adverse events, and unresolved issues of EUS-GBD in MDBO. The supporting evidence is predominantly observational. Published meta-analyses report technical success generally exceeding 90%, pooled clinical success of approximately 82-89%, and overall adverse event rates of approximately 10-14%; these estimates vary with study selection, outcome definitions, assessment time points, and predominantly observational study designs. Comparative studies suggest efficacy and safety similar to EUS-guided choledochoduodenostomy after failed ERCP in anatomically selected patients, although nonrandomized allocation and confounding by indication remain major limitations. A prospective study has demonstrated feasibility as primary palliation, but this strategy cannot yet be considered standard of care. Prophylactic EUS-GBD to prevent post-stenting cholecystitis represents a separate indication and should not be conflated with EUS-GBD for biliary decompression. The key determinant of physiological success is unobstructed communication between the gallbladder and the central biliary tree; therefore, cystic duct patency, tumor relationship to the cystic duct take-off, gallbladder distension, and the absence of extensive gallbladder involvement must be assessed before intervention. EUS-GBD is best positioned as a rescue option after failed ERCP when direct EUS-BD is technically impossible, unsafe, or unsuccessful. Prospective randomized trials, standardized outcome definitions, comparative cost-effectiveness analyses, and dedicated long-term stent management protocols are needed before broader adoption.