Published online Jul 21, 2021. doi: 10.3748/wjg.v27.i27.4429
Peer-review started: January 28, 2021
First decision: February 24, 2021
Revised: February 28, 2021
Accepted: April 25, 2021
Article in press: April 25, 2021
Published online: July 21, 2021
Multifocal-type autoimmune pancreatitis (AIP), sometimes forming multiple pancreatic masses, is frequently misdiagnosed as pancreatic malignancy in routine clinical practice. It is critical to know the imaging features of multifocal-type AIP to prevent misdiagnosis and unnecessary surgery. To the best of our knowledge, there have been no studies evaluating the value of diffusionweighted imaging (DWI), axial fat-suppressed T1 weighted image (T1WI), and dynamic contrast enhanced-computed tomography (DCE-CT) in detecting the lesions of multifocal-type AIP.
The key issue is whether CT and magnetic resonance imaging features of multifocal-type AIP can help definitively distinguish from pancreatic ductal adenocarcinoma (PDA) and whether there is an optimal modality to identify pancreatic lesions as correctly as possible. The results will provide important information on the diagnostic performances of DWI, axial fat-suppressed T1WI, and DCE-CT and the key imaging features for differentiating multifocal-type AIP from PDA.
We aimed to clarify the exact prevalence and radiological findings of multifocal AIP in our cohorts and compare the sensitivity of DWI, axial fat-suppressed T1WI, and DCE-CT for detecting AIP lesions. We also compared radiological features between multifocal AIP and PDA with several key imaging landmarks.
Twenty-six patients with proven multifocal AIP were retrospectively included. Two blinded independent radiologists rated their confidence level in detecting the lesions on a 5-point scale and assessed the diagnostic performance of DWI, axial fat-suppressed T1WI, and DCE-CT. CT and magnetic resonance images of multifocal AIP were systematically reviewed for typical imaging findings and compared with the key imaging features of PDA.
Among 118 patients with AIP, 26 (22.0%) had multiple lesions (56 lesions). Ulcerative colitis was associated with multifocal AIP in 7.7% (2/26) of patients, and Crohn’s disease was associated in 15.3% (4/26) of patients. In multifocal AIP, multiple lesions, delayed homogeneous enhancement, multifocal strictures of main pancreatic duct, capsule-like rim, lower apparent diffusion coefficient values, and elevated serum Ig4 Level were observed significantly more frequently than in PDA, whereas the presence of capsule-like rim in multifocal-type AIP was lower in frequency than total AIP. Of these lesions of multifocal AIP, DWI detected 89.3% (50/56) and 82.1% (46/56) by the senior and junior radiologist, respectively.
Multifocal AIP is not as rare as previously thought and was seen in 22% of our patients. The diagnostic performance of DWI for detecting multifocal AIP was best followed by axial fat-suppressed T1WI and DCE-CT.
Larger and longer term prospective studies to investigate the important radiological findings for differential diagnosis between multifocal AIP and PDA should be performed in future studies.