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Annular pancreas

Chandrashekhar Thukral, MD, PhD
Steven D Freedman, MD, PhD
Section Editor
David C Whitcomb, MD, PhD
Deputy Editor
Shilpa Grover, MD, MPH, AGAF


Annular pancreas is a rare congenital abnormality characterized by a ring of pancreatic tissue surrounding the descending portion of the duodenum. It is thought to originate from incomplete rotation of the ventral pancreatic bud. This topic will review the pathogenesis, clinical manifestations, diagnosis, and management of annular pancreas. Other causes of duodenal obstruction and congenital abnormalities of the pancreas, including pancreas divisum, are discussed in detail, separately. (See "Intestinal malrotation in children" and "Intestinal atresia" and "Pancreas divisum: Clinical manifestations and diagnosis".)


The exact prevalence of annular pancreas is unclear as many individuals with annular pancreas are asymptomatic. In autopsy series in which duodenal dissection has been performed, the prevalence of annular pancreas ranges from 5 to 15 per 100,000 adults [1-3]. Annular pancreas has been associated with maternal polyhydramnios and congenital abnormalities such as Down syndrome, esophageal and duodenal atresia, imperforate anus, and Meckel's diverticulum [4-6]. (See "Down syndrome: Clinical features and diagnosis" and "Intestinal atresia" and "Meckel's diverticulum".)


The pancreas develops from one dorsal and two ventral buds that first appear as evaginations of the primitive foregut at around the fifth week of gestation. Due to selective expansion of the duodenum, by approximately the seventh week, the ventral bud rotates with the gut, passing behind the duodenum from the right to left and eventually fusing with the dorsal bud. The ventral bud forms the inferior part of the head of the pancreas and the uncinate process, whereas the dorsal bud becomes the tail and the body. Fusion of the ductular network of the two buds gives rise to the main pancreatic duct. The accessory pancreatic duct, which often persists, is derived from the dorsal pancreatic duct proximal to the site of fusion (figure 1) [7-9].

Annular pancreas results from failure of the ventral bud to rotate with the duodenum, causing envelopment of duodenum. Three major theories have been proposed to explain the development of annular pancreas:

Adherence of the ventral bud to the duodenal wall prior to rotation, resulting in its persistence and encirclement of the duodenum (Lecco's theory) [10].

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Literature review current through: Oct 2017. | This topic last updated: Mar 29, 2017.
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