Published online Nov 7, 2014. doi: 10.3748/wjg.v20.i41.15177
Revised: May 11, 2014
Accepted: July 22, 2014
Published online: November 7, 2014
Current understanding of autoimmune pancreatitis (AIP) recognizes a histopathological subtype of the disease to fall within the spectrum of IgG4-related disease. Along with clinical, laboratory, and histopathological data, imaging plays an important role in the diagnosis and management of AIP, and more broadly, within the spectrum of IgG4-related disease. In addition to the defined role of imaging in consensus diagnostic protocols, an array of imaging modalities can provide complementary data to address specific clinical concerns. These include contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging for pancreatic parenchymal lesion localization and characterization, endoscopic retrograde and magnetic resonance cholangiopancreatography (ERCP and MRCP) to assess for duct involvement, and more recently, positron emission tomography (PET) imaging to assess for extra-pancreatic sites of involvement. While the imaging appearance of AIP varies widely, certain imaging features are more likely to represent AIP than alternate diagnoses, such as pancreatic cancer. While nonspecific, imaging findings which favor a diagnosis of AIP rather than pancreatic cancer include: delayed enhancement of affected pancreas, mild dilatation of the main pancreatic duct over a long segment, the “capsule” and “penetrating duct” signs, and responsiveness to corticosteroid therapy. Systemic, extra-pancreatic sites of involvement are also often seen in AIP and IgG4-related disease, and typically respond to corticosteroid therapy. Imaging by CT, MR, and PET also play a role in the diagnosis and monitoring after treatment of involved sites.
Core tip: The imaging appearance of autoimmune pancreatitis (AIP) varies widely. The literature is reviewed for imaging characteristics that favor a diagnosis of AIP rather than differential considerations such as pancreatic cancer. Response to steroid therapy and the presence of extra-pancreatic lesions are often seen in AIP and in IgG4-related disease. Extra-pancreatic findings and the role of imaging in monitoring their response to therapy are also reviewed, including recent developments in positron emission tomography imaging.