Acute pancreatitis caused by a duodenal duplication cyst covering the ampulla of Vater

Duodenal duplication cyst is not a common congenital anomaly and the pathophysiology may become very complicated if the cyst is situated at the ampulla of Vater. Here we report a very rare female case of duodenal duplication cyst at the ampulla of Vater, which caused acute pancreatitis due to massive protein plaques in the pancreatic duct. She had a past history of double duodenal atresia and underwent surgery as a neonate. The correct diagnosis could not be determined before the second operation at four years of age and the exact pathophysiology finally became apparent during the operation with a contrast medium study and duodenotomy. We discuss the complicated clinical features and diagnostic and treatment procedures before and during the operation.