Annular pancreas is a congenital anomaly in which pancreatic tissue encircles the second part of the duodenum, potentially causing partial or complete duodenal obstruction (atresia). It is due to abnormal migration of the ventral pancreatic bud.

According to Rumack’s Diagnostic Ultrasound:

“Annular pancreas results from failure of the ventral pancreatic bud to rotate properly, leading to encirclement of the duodenum.”