A new embryological theory of the pancreatic duct system.

BACKGROUND/AIMS To clarify the anatomy of the pancreatic duct system and to investigate its embryology. METHODS We reviewed pancreatograms of 256 patients with a normal pancreatic head and 36 cases of complete pancreas divisum. RESULTS Accessory pancreatograms were divided into two patterns. The long-type accessory pancreatic duct (APD) forms a straight line and joins the main pancreatic duct (MPD) at the neck portion of the pancreas. The short-type APD joins the MPD near its first inferior branch. The short-type APD is less likely to have a long inferior branch arising from the APD. The length of the APD from the orifice to the first long inferior branch was similar in the short- and long-type APD. The first long inferior branch from the long-type APD passes through the MPD near the origin of the inferior branch from the MPD. Immunohistochemically, in the short-type APD, the MPD between the junction of the short-type APD and the neck portion originated from the ventral pancreas. CONCLUSION The long-type APD represents a continuation of the main duct of the dorsal pancreatic bud. The short-type APD is very likely formed by the proximal main duct of the dorsal pancreatic bud and its long inferior branch, with the main duct of the dorsal pancreatic bud at the point of connection with the main duct of the ventral pancreatic bud being obliterated and replaced by this additional communication.