CT and MR imaging features of fistulas from intraductal papillary mucinous neoplasms of the pancreas to adjacent organs: A retrospective study of 423 patients.

PURPOSE: The objectives of this study were to determine the frequency with which intraductal papillary mucinous pancreatic neoplasms (IPMNs) show fistulization to adjacent organs and to describe the multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI) findings for this specific complication. METHODS: A retrospective analysis of the clinical and imaging files of all patients with IPMNs who were followed over 8 years by our department was performed to identify those with fistula formation. Two radiologists determined the type of IPMN, the number and size of visible fistulas, the involved adjacent organs, the pancreatic location and the presence of imaging findings suggestive of malignant transformation of the IPMN. Histological correlation was also performed. RESULTS: A total of 423 patients were included. Fistula formation was present in 8 patients (1.9%). The corresponding IPMNs were of the main duct type (n=4; 50%), the branch duct type (n=1; 13%) or the mixed type (n=3; 38%). In half of the cases, these tumors were discovered incidentally. A total of 26 fistulas (1-7 per patient) were identified. These fistulas involved the duodenum (65.4%), stomach (19.2%), common bile duct (11.5%) and colon (3.8%). All patients had fistulas to the duodenum. All fistulas appeared to develop from a malignant IPMN based on the imaging studies, but two of the five available samples did not exhibit atypia (a quarter of all fistulas). In 50% of cases, the IPMN was of the intestinal form. CONCLUSIONS: Fistulas are uncommon complications of IPMNs, regardless of malignant transformation of the IPMNs. Fistulas appear to predominate among malignant main-duct IPMNs, are generally multiple and affect several organs, and their preferential target is the duodenum. However, fistulas do not adhere to a strict criterion of malignancy.