- Embyrologic deformity of the pancreas
- Pancreas normally develops from one dorsal and two ventral buds
- Ventral buds normally rotate with duodenum, but if they fail to do so, annular pancreas may form
- Three theories to explain this:
- Adherence of the ventral bud to the duodenal wall prior to rotation, resulting in its persistence and encirclement of the duodenum (Lecco's theory).
- Persistence and enlargement of the left ventral bud (Baldwin's theory).
- Hypertrophy and fusion of the ventral and dorsal buds before rotation of the gut, resulting in complete encirclement of the duodenum.