Pancreatic suppurative process: a rare case of pancreatoduodenal fistula with an intraductal papillary mucinous neoplasm

Background: Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas are cystic lesions that arise from the proliferation of mucin-secreting cells within the pancreatic ducts. Representing approximately 20% of pancreatic neoplasms and 5% of pancreatic cystic lesions, incidental diagnosis of IPMNs has increased with advanced imaging techniques. A rare but noteworthy complication of IPMN is the development of fistulas to adjacent organs, most commonly involving the duodenum. This report presents a unique case of a pancreatoduodenal fistula secondary to an obstructive pancreatic stone in a patient with IPMN. It highlights the diagnostic challenges and clinical presentation of this condition, alongside successful endoscopic management. This case aims to increase clinician awareness of such complications and add to the existing literature on the mechanisms of fistula formation in IPMN. Case Description: An 82-year-old male with history of hypertension, pulmonary fibrosis, pancreas divisum, and main duct IPMN (MD-IPMN) diagnosed five years ago, presented lower extremity weakness. Laboratory examination revealed leukocytosis and elevated C-reactive protein. Abdominal magnetic resonance imaging (MRI) with contrast showed a 25 mm MD-IPMN in the pancreatic head and a pancreatic stone obstructing minor papilla. Endoscopic retrograde cholangiopancreatography (ERCP) revealed thick mucinous purulent secretion from minor papilla and an ulcerated fistula in second part of duodenum, communicating with MD-IPMN containing a large pancreatic stone. A double pigtail plastic stent was placed to facilitate drainage. Patient had a favorable recovery and was discharged 24 hours post-procedure. Conclusions: IPMN are rare pancreatic tumors, and fistulization is an infrequent complication. When complications occur, they typically involve ductal dilation, pancreatitis, hemorrhage, abscesses, or perforation. Fistulas develop in 1.9–6.6% of complicated IPMN cases, predominantly towards duodenum, common bile duct, and stomach. Development of fistulas may result from malignant invasion, elevated intraductal pressures, mechanical penetration, or inflammation. In this case, presence of an obstructive pancreatic stone was the primary factor for increased intraductal pressure leading to pancreatoduodenal fistula.