Abstract
Severe acute pancreatitis (SAP) is a special type of acute pancreatitis (AP), often accompanied by systemic and local complications, and is an acute abdominal condition characterized by severe illness, multiple complications, and high mortality. The complex pathophysiological mechanisms of SAP pose great challenges to its clinical diagnosis and treatment. On December 24, 2021, a patient with SAP was admitted to the General Surgery Department of Xiangya Hospital, Central South University. Through CT, magnetic resonance cholangiopancreatography (MRCP), T-tube cholangiography, and choledochoscopy, a special anatomical communication between the pancreatic segment of the common bile duct and pancreatic walled-off necrosis was finally identified, indicating the formation of a biliary internal fistula. This key finding provided crucial clues for precise diagnosis and guided the formulation of an individualized treatment strategy, highlighting the importance of recognizing special anatomical relationships in complex SAP cases. Through multidisciplinary collaborative management and timely intervention, the patient's condition was ultimately well controlled. This case alerts clinicians to the rare anatomical abnormality of SAP complicated with biliary internal fistula, emphasizes the combined application of imaging and endoscopic examinations, and advocates individualized diagnosis and treatment plans based on multidisciplinary collaboration, so as to improve the diagnostic and therapeutic efficiency and prognostic outcomes of such complex severe cases.