Annular pancreas: emphasis on magnetic resonance cholangiopancreatography findings.

An annular pancreas is a rare congenital anomaly in which a portion of the pancreatic tissue surrounds the duodenum. Magnetic resonance cholangiopancreatography (MRCP) is used extensively for evaluating the pancreatobiliary ducts. There have been only few cases in which MRCP clearly demonstrated the types of annular ducts, however. Two cases of an annular pancreas based on a new classification of the morphologic type are reported.