Post-ERCP pancreatogastric fistula associated with an intraductal papillary-mucinous neoplasm of the pancreas – a case report and literature review

BACKGROUND: Fistula formation has been reported in intraductal papillary-mucinous neoplasms (IPMNs) with or without invasion of the adjacent organs. The presence or absence of invasion is mostly determined by postoperative histological examination rather than by preoperative work-up. CASE PRESENTATION: A 72 year-old Japanese woman showed remarkable dilatation of the main pancreatic duct (MPD) in the distal region of the pancreas. Subsequent ERCP also showed MPD dilatation, after which the patient suffered moderate pancreatitis. A subsequent gastroscopy revealed a small ulceration that had not been observed in a gastroscopy performed 3 months prior. Mucinous discharge from the ulceration suggested it might be the orifice of a fistula connected to the MPD. En bloc resection including the distal region of the pancreas, spleen, stomach and part of the transverse colon was performed under the pre- and intraoperative diagnosis of an invasive malignant IPMN. However, histopathology revealed the lesion to be of "borderline malignancy" without apparent invasion of the stomach. Light microscopy showed inflammatory cellular infiltrates (mainly neutrophils) around the pancreatogastric fistula, but there was no evidence of neoplastic epithelia lining the fistulous tract. CONCLUSION: This case highlights that a pancreatogastric fistula can develop after acute inflammation of the pancreas in the absence of cancer invasion. Further information regarding IPMN-associated fistulae is necessary to clarify the pathogenesis, diagnosis, appropriate surgical intervention and prognosis for this disorder.