Annular pancreas: a review of its molecular embryology, genetic basis and clinical considerations

The annular pancreas remains an intriguing congenital anomaly. Many theories have sought to explain its embryological basis; however, no consensus has yet been reached regarding the exact mechanism of aberration. More recently, molecular investigations have shed light on some of these theories, confirming the origination of annular tissue from the ventral pancreatic bud. These studies highlight the role of the hedgehog signaling pathway in the development of this anomaly. Overexpression of the ventral-specific gene transmembrane 4 superfamily member 3 (tm4sf3) has also been associated with annular formation. Moreover, isolated case reports of familial annular pancreas have also been documented, suggesting a genetic basis for the development of this anomaly. Annular pancreas can initially present in childhood or adulthood with symptoms of duodenal obstruction and is diagnosed using a variety of imaging modalities. Treatment usually involves surgical correction, with bypass procedures (e.g. duodenoduodenostomy, gastrojejunostomy or duodenojejunostomy) currently favored over annular resection due to complications associated with the latter approach.