Imaging findings of IgG4-related autoimmune pancreatitis

Abstract

Objective To analyze the computed tomography (CT) and magnetic resonance imaging (MRI) findings of immunoglobulin G4 (IgG4)-related autoimmune pancreatitis (AIP), to improve the understanding of the imaging features of this disease, and to reduce imaging misdiagnosis. Methods A retrospective analysis was performed on the clinical data of 47 patients with IgG4-related AIP, among whom 33 underwent plain CT scan and contrast-enhanced CT scan, 24 underwent plain MRI scan, contrast-enhanced MRI scan, and magnetic resonance cholangiopancreatography (MRCP) examination, and 10 underwent combined CT and MRI examination to observe the morphology, changes in density/signal, contrast enhancement characteristics of the diseased pancreas, the peripancreatic and pancreatic duct changes, and the manifestations out of the pancreas. Results The CT and MRI scans showed that among the 47 patients, 27 had a “sausage-like”, diffusely enlarged pancreas and 20 had a focally enlarged pancreas. The plain CT scan showed a uniform and slightly low density; the contrast-enhanced CT scan of the lesion showed an inhomogeneous patchy enhancement in arterial phase, and a uniformly delayed progressive enhancement in portal vein phase and delayed phase. The MRI scan of the lesion showed inhomogeneous and slight hypointensity on T1WI-FS and slight hyperintensity on T2WI, the contrast-enhanced MRI scan showed an inhomogeneous mild enhancement in the early stage and a uniformly delayed progressive enhancement on delayed scan. The CT and MRI scans showed that 28 patients had capsule-like edges around the panc-reas, namely “capsule sign”, with a mild to moderate delayed enhancement on contrast-enhanced images. The MRCP showed that 10 patients had segmental stenosis of the main pancreatic duct and localized mild dilatation of the upstream pancreatic duct. The CT and MRI scans showed that 30 patients had changes in the bile duct system, with wall thickening, stenosis, and delayed enrichment of the pancreatic segment of common bile duct. The MRCP showed “beak-like” changes, and dilatation of upstream intrahepatic and extrahepatic bile ducts to varying degrees. Conclusion The CT and MRI findings of IgG4-related AIP have certain characteristics. The combination of imaging findings and relevant laboratory tests can help improve the diagnosis of this disease.

Keywords

• autoimmune pancreatitis|immunoglobulin g4-related disease|tomography, x-ray computed|magnetic resonance imaging|diagnosis