Annular Pancreas in Adults

OBJECTIVE: The purpose of this study was to review the CT, MRI, and ERCP findings of annular pancreas in adults. MATERIALS AND METHODS: A search of the radiology and ERCP databases at our institution for cases of annular pancreas in adults yielded the records of 42 patients who underwent 29 ERCP, 22 CT, and 13 MRI examinations. The CT and MR images were reviewed by two readers, and consensus agreement was reached regarding the shape of the pancreas, anatomic configuration of the ducts, and presence of disease. In addition, the degree of encirclement of the second part of the duodenum by the pancreatic head was evaluated in 24 patients with the CT or MRI finding of annular pancreas and in 30 control patients who were found not to have annular pancreas at ERCP. RESULTS: Nine of 24 (37.5%) cases of annular pancreas detected with CT or MRI did not have a radiologically complete ring of pancreatic tissue surrounding the second part of the duodenum. Three of the nine patients (33%) with radiologically incomplete annular pancreas and six of the 15 patients (40%) with complete annular pancreas had gastric outlet obstruction (p = 0.75). The presence of pancreatic tissue posterolateral to the second part of the duodenum had a high sensitivity (92%) and specificity (100%) for the presence of annular pancreas. The rates of pancreas divisum (37%) and chronic pancreatitis (48%) were high in this cohort. CONCLUSION: Annular pancreas can be diagnosed without the finding of a radiologically complete ring of pancreatic tissue. A crocodile jaw configuration of pancreatic tissue is suggestive of the presence of annular pancreas.