Groove pancreatitis: report of a case and review of the clinical and radiologic features of groove pancreatitis reported in Japan.

We report a case of groove pancreatitis in which a hypoechoic mass between the duodenum and pancreas head was clearly imaged, and narrowing of the supra-ampullary area of the duodenum and bile duct stenosis were also found. The diagnosis was confirmed by surgery. Microscopic examination showed extensive scarring between the duodenum and pancreas head. Protein plugs were found in Santorini's duct. We consider that the disturbance of the pancreatic juice outflow in Santorini's duct is one of the important pathogenic factors in the development of groove pancreatitis. Therefore, we emphasize the finding of Santorini's duct in the differential diagnosis of groove pancreatitis.