An accessory pancreas was found near the origin of the inferior mesenteric artery in an 11-year old boy. The size of these masses varies in diameter, from a few millimeters to 5cm and their own ducts. The masses may contain pancreatic islet cells. They are most common in the duodenum. Pancreatic divisum occurs in development when the dorsal and ventral parts of the pancreas fail to fuse so that the drainage of the gland is mainly through the accessory papilla.
Autopsy studies suggest that pancreas divisum is the most common congenital variation of the organ.
Divided pancreas differs from the accessory in that a mass of the pancreas becomes separated from the main gland, connected only by a duct. It may be transverse, ascending, or bent in various ways. Numerous variations in the ducts can be understood from their complicated development. The accessory pancreatic duct in the fetus is as large as the pancreatic duct, the preponderance of the latter being established later. The accessory duct in the adult may be larger than usual, and retain its primitive drainage, or even drain the entire gland in rare cases where the pancreatic duct is absent.