BACKGROUND: Cystic lesions on the pancreatic head can mimic fluid-filled duodenal or periampullary diverticula. We reviewed a series of cases in which periampullary diverticula were misdiagnosed as cystic pancreatic lesions.

CASE REPORT: Case 1. A Chinese woman presented to the surgical outpatient clinic for intermittent upper abdominal discomfort. Contrast-enhanced MRI of the abdomen revealed a cystic-appearing lesion in the region of the pancreatic head, which was reported as a cystic pancreatic lesion. A follow-up scan showed this lesion to be filled with fluid, gas, and debris, suggestive of a periampullary diverticulum. Review of a prior CT scan confirmed a periampullary diverticulum. Case 2. A Chinese man with a history of chronic hepatitis B infection underwent an MRI of the liver, which revealed a cystic-appearing lesion in the region of the pancreatic head, reported as a cystadenoma or pseudocyst. The patient underwent an endoscopic ultrasound. A large periampullary diverticulum was discovered but there was no pancreatic head lesion. Case 3. A Chinese woman with a history total hysterectomy and bilateral salpingo-oophorectomy for ovarian malignancy underwent an MRI of the abdomen and pelvis. A cystic-appearing lesion was found in the region of the pancreatic head, which was reported as a cystadenoma or intraductal papillary mucinous neoplasm. Follow-up magnetic resonance cholangiopancreatography showed a signal void within, suggestive of gas within a periampullary diverticulum. Review of a prior CT scan showed a periampullary diverticulum.

CONCLUSIONS: Periampullary diverticula, when fluid-filled, can be confused with cystic lesions in the pancreatic head. Radiologists should be aware of this potential pitfall.

Keywords: Diagnostic Errors, Ampulla of Vater, Diverticulum - diagnosis, Duodenal Diseases - diagnosis, Magnetic Resonance Imaging, Pancreatic Cyst - diagnosis