MRI/MRCP and endoscopic ultrasound in pancreatobiliary disease: defining complementary roles in diagnostic and therapeutic decision-making.

MRI and magnetic resonance cholangiopancreatography (MRCP) remain foundational techniques for the evaluation of pancreatobiliary disease because they provide a comprehensive, non-invasive assessment of the pancreatic parenchyma, biliary tree and surrounding structures. With optimized protocols, MRI/MRCP has high diagnostic performance for biliary obstruction, pancreatic cystic lesions and many inflammatory or neoplastic pancreatic disorders. Nevertheless, selected clinical scenarios remain challenging when findings are equivocal, discordant with biochemical or clinical suspicion, or insufficient to guide intervention. Endoscopic ultrasound (EUS) should therefore be understood not as a replacement for MRI/MRCP, but as a complementary problem-solving modality. Its incremental value is greatest when a specific unresolved question remains after cross-sectional imaging and when the result is likely to change management. Beyond high-resolution proximity-based imaging, EUS can provide tissue acquisition, cyst fluid analysis, molecular testing, contrast-enhanced assessment, elastography and selected therapeutic interventions. This revised review defines the complementary roles of MRI/MRCP and EUS in pancreatobiliary disease, with emphasis on small solid pancreatic lesions, pancreatic cystic lesions, pancreaticobiliary microlithiasis, autoimmune pancreatitis mimics, and therapeutic EUS applications. We also discuss MRI/MRCP protocol optimization, emerging deep learning-based MRI reconstruction, and the limitations of EUS in altered anatomy, gastric outlet obstruction, pancreatic tail lesions and multifocal neuroendocrine tumors. A practical selective imaging pathway is proposed to support clinically driven decision-making.