A rare ring-shaped anomaly of the main pancreatic duct accompanying a branch duct IPMN.

The patient was a 74-year-old female. Screening computed tomography for examination of the abdomen showed a cystic mass in the pancreatic body. Close investigation using endoscopic retrograde cholangiopancreatography and magnetic resonance cholangiopancreatography revealed a very rare finding: the main pancreatic duct bifurcated at the pancreatic body, and these two ducts converged at the caudal side. A multilocular cystic mass in the pancreatic body and mucus discharge from the orifice of major papilla were observed. There was no protruded lesion in the main pancreatic duct. No findings suggested apparent malignancy. The patient was diagnosed as having hyperplastic intraductal papillary mucinous neoplasm of branch type showing a ring-shaped pancreatic duct, and was placed under follow-up.