MR imaging and MR cholangiopancreatography of multifocal intraductal papillary mucinous neoplasms of the side branches: MR pattern and its evolution

Purpose. This paper describes the magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) pattern of multifocal intraductal papillary mucinous tumours (IPMT) of the pancreatic side branches and its evolution during follow-up. Materials and methods. Twenty-six patients with multifocal IPMT of the side branches were included in this retrospective study. Inclusion criteria were >= 2 ectasic side branches, presence of communication with the main pancreatic duct, and >= 2 MRI/MRCP examinations after >= 6-12 months. Exclusion criteria were IPMT involving both the main pancreatic duct and its branch ducts, previous surgery and lack of follow-up MRI examinations. Median follow-up was 27 (range 6-59) months. Images were assessed qualitatively and quantitatively. Qualitative assessment considered: the number of cystic lesions of the branch ducts, morphology of the communication between the cystic lesion and the main duct (direct or neck), presence of intraluminal filling defects within the cystic lesions, presence of mural nodules and mural enhancement of the cystic lesion. Quantitative assessment considered mean maximal diameter of the cystic lesions and mean length of the communication neck. Results. At diagnosis, the mean number of cystic lesions of the side branches was 7.5. A communication neck was detected in 16/26 patients (60%). Intraluminal filling defects in the side branches were present in 6/26 patients (23%). Mural nodules were seen in 1/26 patients (4%). The mean diameter of the cystic lesions was 18.8 mm. The mean length of the communication neck was 6.9 mm. At follow-up, the mean number of cystic lesions of the side branches was 8.4. A communication neck was detected in 20/26 patients (77%). Intraluminal filling defects in the side branches were detected in 7/26 patients (27%); mural nodules were seen in 2/26 patients (8%). Mural enhancement of the branch duct was detected in 2/26 patients (8%). The mean diameter of the cystic lesions increased to 22.3 rum (p < 0.05), and the mean length of the communication neck was 8.6 mm. Conclusions. Multifocal IPMT of the side branches shows a constant but very slow progression over time. In our series, only 2/26 patients showed mural nodules.