A Classification of Procedural Complexity in Therapeutic Endoscopic Ultrasound: Rationale and Implications for Practice and Training.

BACKGROUND: Therapeutic endoscopic ultrasound (TEUS) has expanded into a broad procedural platform including access, delivery, measurement, ablation, drainage, and anastomoses. Nevertheless, TEUS lacks a shared procedural complexity classification. METHODS: Within an International initiative of the Next Generation EUS group, a dedicated task force developed a four-level classification, subsequently evaluated through Delphi methodology. The classification considered target stability and size, accessory exchange, adverse event profile, technical standardization, and prerequisite skills. To support and contextualize the consensus output, a targeted narrative review of published evidence was performed, analyzing technical success, clinical success, adverse events, learning curves, and procedural modifiers across major TEUS procedures. RESULTS: The Delphi-informed classification achieved 92.7% agreement among 106 respondents. Level 1 includes procedures mainly based on endosonographic skills, such as EUS-guided ablation and placement of Lumen Apposing Metal Stents (LAMS) within large fluid collections; Level 2 includes EUS-guided choledochoduodenostomy and gallbladder drainage with LAMS and fluid collection drainage with multistep plastic stenting; Level 3 includes more demanding fluoroscopy-based interventions, such as EUS-guided hepaticogastrostomy, rendezvous, and upper gastrointestinal anastomoses; Level 4 includes procedures with advanced complexity and limited standardization, such as EUS-directed ERCP, pancreatic duct drainage, and small/large bowel anastomoses. This article discusses the rationale, clinical utility, and training implications of this classification. CONCLUSIONS: This 4-level Delphi-informed classification for TEUS complexity achieved high expert agreement and provides a pragmatic framework to support training pathways, case selection, outcome interpretation, referral, and credentialing processes.