Annular pancreas can be extramural or intramural. In the extramural type, the ventral pancreatic duct encircles the duodenum to join the main pancreatic duct. In the intramural type, the pancreatic tissue is intermingled with the duodenal wall muscle and small pancreatic ducts drain directly into the duodenum.
Patients with extramural annular pancreas can present with high gastrointestinal obstruction, sometimes with pancreatitis. Patients with intramural annular pancreas can present with symptoms of duodenal ulceration.
Contrast fluoroscopy can suggest the diagnosis by revealing narrowing at the level of the major papilla. ERCP or MRCP can show the duct of Wirsung encircling the duodenum in the patient with extramural annular pancreas. Cross sectional imaging will show pancreatic tissue around the second portion of the duodenum, as shown above in two patients with annular pancreas.
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