This portion of the pancreas can constrict the duodenum and block or impair the flow of food to the rest of the intestines.

[2] Early signs of abnormality include polyhydramnios (an excess of amniotic fluid), low birth weight, and feeding intolerance immediately after birth, in particular a tendency to develop epigastric distention associated with non-biliary vomiting (the obstruction is generally above the papilla of Vater, therefore superior to the junction with the bile ducts).

Abdominal radiography can show the classic sign of the "double bubble": the presence of air in the stomach and duodenum.

[5][6] Unfortunately, this double-bubble sign is not pathognomonic for annular pancreas, as it can also be observed in other conditions, such as duodenal atresia[7] and intestinal malrotation.

An abdominal CT scan or an MRI allows to highlight the narrowing of the descending duodenal tract and the ring of pancreatic tissue surrounding the duodenum: this ring can be complete or, in patients with an incomplete annular pancreas, extended in a postero-lateral or anterolateral direction with respect to the second part of the duodenum.