S3318 From Drainage to Dilemma: A Complex Journey Through Pancreatic Pseudocyst Fistulization, Necrosis, and Duodenal Stenosis

Introduction: Pancreatic pseudocysts are common sequelae of acute or chronic pancreatitis, occurring in up to 40% of cases. Endoscopic ultrasound (EUS)-guided cystogastrostomy using lumen-apposing metal stents (LAMS) has emerged as a minimally invasive, effective technique for symptomatic or infected collections. We describe a rare case of pancreatico-duodenal and pancreatico-colonic fistulization following endoscopic ultrasound-guided drainage of walled-off pancreatic necrosis (WON). Case Description/Methods: A 59-year-old man with a history of type 2 diabetes mellitus, hypertriglyceridemia, non-alcoholic fatty liver disease, and prior pancreatitis presented with 2 months of epigastric pain, nausea, vomiting, and unintentional weight loss of 10 kilograms. Magnetic resonance imaging of the abdomen showed a complex fluid collection measuring 19.7 × 6.3 × 6.6 cm in the pancreatic body and tail, consistent with a pseudocyst. Upper endoscopy revealed a gastric phytobezoar and acquired duodenal stenosis. Endoscopic ultrasound-guided cystogastrostomy was performed using a 20 × 10 mm LAMS, dilated to 16.5 mm, with a 10 Fr × 4 cm double pigtail stent placed for internal drainage. Purulent material was observed, and the patient was discharged on empiric antibiotics. The patient was readmitted several days later with watery diarrhea and diffuse abdominal pain. Laboratory results showed leukocytosis, hyponatremia, hypokalemia, and elevated fecal elastase. Computed tomography revealed a reduction in the size of the collection to 9.1 × 2.4 cm with persistent multiloculated components and pancreatic head edema. Repeat endoscopy showed retained necrotic debris and a duodenal fistula, prompting endoscopic necrosectomy. Colonoscopy identified extrinsic stenosis in the splenic flexure. Follow-up imaging confirmed fistulous tracts between the peripancreatic collection and both the duodenum and colon. Serial imaging later demonstrated resolution of the collection. The stents were removed, and the patient showed clinical improvement with weight gain and symptom resolution. Discussion: Pancreatico-enteric fistulization is a rare (3%–10%) but serious complication of pancreatic pseudocysts and WON. This case illustrates the potential for fistula formation even with appropriate endoscopic ultrasound-guided drainage and underscores the need for close monitoring. Endoscopic therapy remains a viable and effective strategy for managing such complex cases.