Three-dimensional computed tomography pancreatography of an annular pancreas with special reference to embryogenesis

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.

Prenatal diagnosis of annular pancreas: reliability of the double bubble sign with periduodenal hyperechogenic band

OBJECTIVE

To evaluate the power of prenatal 2-D ultrasound examination in the 2nd trimester as a method of choice for accurate diagnosis of annular pancreas.

METHODS

Co-incidence of the double bubble sign (often accompanying gastroduodenal dilatation) together with a hyperechogenic band around the duodenum (corresponding with the tissue of annular pancreas) was used as a diagnostic criterion. Findings from postnatal surgery served for verification.

RESULTS

From 7,897 screened pregnancies, annular pancreas was proven in the cases where both signs were present, but never without the hyperechogenic band (N(1) = 3, N(2) = 3, p < or = 0.05). Sensitivity and specificity were 100%.

CONCLUSIONS

More multicentric studies are required to test this approach. The following diagnostic strategy is reasonable at the present time: when the double bubble sign is discovered, always suspect annular pancreas and look for the second sign: hyperechogenic bands around the duodenum. Also look for known associated anomalies, and vice versa, if any of associated anomalies are noted, also search specifically for the signs of annular pancreas.