S3630 Resolution of Large Cystoduodenal Fistula With Conservative Management in a Patient Status Post Treatment of Walled-Off Necrotizing Pancreatitis

Introduction: Spontaneous cystogastric and cystoduodenal fistulas are rare complications of pancreatitis. We present a case of an unusually large (>7 cm) spontaneous cystoduodenal fistula in the setting of pancreatitis with complete resolution with conservative management. Case Description/Methods: A 41-year-old man with a prior history of necrotizing pancreatitis secondary to alcohol use complicated by walled-off necrosis in the pancreatic tail who underwent endoscopic ultrasound-guided cystgastrostomy with serial necrosectomies and endoscopic retrograde cholangiopancreatography (ERCP) with pancreatic duct placement at our institution. He had his cystgastrostomy stent replaced with plastic double pigtail cystgastrostomy stents after resolution of necrosis but was lost to follow-up for >1 year before re-presenting with abdominal pain and recurrent pancreatitis. On magnetic resonance cholangiopancreatography (MRCP) at that time, he had notable thickening of the duodenal sweep, acute on chronic pancreatitis changes with retained PD stent. He subsequently underwent ERCP, with a large >7 cm ulcerated fistula tract in the duodenal sweep. The pancreatic duct stent was removed, and a pancreatogram obtained showed direct communication with the ventral pancreatic duct in the neck of the pancreas to the fistula draining into the duodenum. Given adequate pancreatic duct drainage and absence of leak or stricture, no pancreatic duct stent was replaced. Fistula biopsies demonstrated ulcerative exudate without malignancy. The patient was discharged, and on follow-up esophagogastroduodenoscopy and EUS 6 weeks later, he was noted to have complete resolution of the fistula tract with a small area of residual scarring in the duodenal wall. The patient underwent EUS celiac plexus block with significant improvement of his pain and was able to wean off pain medications. Discussion: Spontaneous cystoduodenal fistula is a rare complication of pancreatitis. In the case presented, we suspect the patient had spontaneous rupture of a large pseudocyst into the duodenal wall, which resulted in the formation of an unusually large cystoduodenal fistula in the duodenal sweep. The management and long-term clinical outcomes remain ill-defined due to rarity of spontaneous pancreatitis-related fistula. Management of spontaneous cystogastric or cystoduodenal fistula should be individualized based on the size of the residual cystic cavity and the presence of necrosis. In the absence of significant necrosis or residual cyst cavities, these fistulae may heal with conservative management as demonstrated in our case.