Background/objectives: As intraductal papillary mucinous neoplasm (IPMN) of the pancreas is associated with acute pancreatitis (AP) in some cases, predicting the risk of pancreatitis is as important as predicting the risk of malignancy in IPMN cases. In this study, we attempted to clarify the characteristics of IPMN associated with AP, compared to those of IPMN not associated with AP. Methods: From January 2006 to March 2013, data from 88 patients who underwent surgery for IPMN were retrospectively investigated and analyzed. We evaluated clinical and pathological variables of each patient and compared patients with IPMN with AP to those without AP. Furthermore, we presented representative cases of mild and severe pancreatitis caused by IPMN. Results: Overall, 12 of 88 patients with IPMN (13.6%) had AP. Seven of the 12 patients had a single episode of AP, whereas the remaining 5 patients were diagnosed with IPMN with repeated AP. Ten of 12 patients with AP were diagnosed with mild AP and the remaining 2 with severe AP. Regarding clinical findings, the proportion of dilated papilla with mucin extrusion was significantly higher in patients with IPMN with AP than in those without AP (p = 0.035). Histological findings indicated that the proportion of intestinal-subtype IPMN was significantly higher in patients with IPMN with AP (p = 0.013). Conclusions: AP caused by IPMN derives mostly from intestinal IPMN. Dilated papilla with mucin extrusion can be a potential predictor of AP.
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