Annular pancreas is a rare condition in which the second part of the duodenum is surrounded by a ring of pancreatic tissue continuous with the head of the pancreas. This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the intestines. It is estimated to occur in 1 out of 12,000 to 15,000 newborns. The ambiguity arises from the fact that not all cases are symptomatic.
It is typically associated with abnormal embryological development, however adult cases can develop. It can result from growth of a bifid ventral pancreatic bud around the duodenum, where the parts of the bifid ventral bud fuse with the dorsal bud, forming a pancreatic ring. It can also result if the ventral pancreatic bud fails to fully rotate, so it remains on the right or if the dorsal bud rotates in the wrong direction, such that the duodenum is surrounded by pancreatic tissue. Blockage of the duodenum develops if inflammation (pancreatitis) develops in the anular pancreas.
^Lainakis N, Antypas S, Panagidis A et al. (2005). "Annular pancreas in two consecutive siblings: an extremely rare case". European Journal of Pediatric Surgery15 (5): 364–8. doi:10.1055/s-2005-865838. PMID16254852.
^Ravitch, MM. (1975). "The pancreas in infants and children". Surg Clin North Am55 (2): 377–85. PMID165579.
^De Ugarte DA, Dutson EP, Hiyama DT (2006). "Annular pancreas in the adult: management with laparoscopic gastrojejunostomy". The American surgeon72 (1): 71–3. PMID16494188.