Heterotopic Pancreatitis with Obstruction of the Major Duodenal Papilla - A Rare Trigger of Obstructive Orthotopic Pancreatitis

Background: Heterotopic pancreas appears in 0.5 to 13% of autopsies. The most frequent locations are stomach, duodenum or upper jejunum. Pancreatitis in heterotopic pancreas is rarely described, and clinical symptoms caused by this heterotopic inflammation are uncommon. Method: We report a case of heterotopic pancreatitis localized in the major duodenal papilla causing biliary obstruction and mimicking a pancreatic head tumor. Clinically and radiologically, malignancy was suspected. Preoperative biopsies showed only fibrosis. A pylorus preserving resection of the pancreatic head was performed followed by an uneventful postoperative course. Result: Macroscopically, in the periampullary region on the pancreatic side a thickened duodenal wall with multiple lobules and cysts was found, compressing the common bile duct. Microscopic examination showed heterotopic pancreas with inflammatory lesions surrounding the ampulla. In the orthotopic pancreas a diffuse chronic pancreatitis with marked inflammation, fibrosis and atrophy of exocrine tissue was found. Conclusion: In our case it was impossible to differentiate between chronic pancreatitis and pancreas carcinoma preoperatively. Radiological findings and endoscopic biopsies were not sufficient to distinguish heterotopic pancreatitis from other tumors of the pancreatic head. Clear diagnosis could only be made by complete histological examinations after pancreatic head resection, being the treatment of choice for pancreatic head tumors of unclear dignity. The differential diagnosis of heterotopic pancreatitis as trigger of unclear enlargement of the pancreatic head is very seldom.