What causes annular pancreas? Annular pancreas is when tissue from the head of the pancreas surrounds the descending duodenum resulting in obstruction.  How does annular pancreas present? Suspect annular pancreas in an infant with bilious vomiting after feeding and a double bubble sign on abdominal x-ray (air in the stomach and duodenum proximal to the obstruction).  Annular pancreas can also present in adulthood and with similar symptoms. This is less common.  Lab findings in annular pancreas? Laboratory testing in patients with annular pancreas reveals: hypochloremic metabolic alkalosis and hypokalemia. Labs: low K, low Cl, high pH.  Imaging findings in annular pancreas? Abdominal x-ray: air in the stomach and proximal duodenum…