Abdominal manifestations of IgG4-related disease: a pictorial review

Abstract

In the last decade, autoimmune pancreatitis has become recognised as part of a wider spectrum of IgG4-related disease, typically associated with elevated serum IgG4 levels and demonstrating a response to corticosteroid therapy. Radiologically, there is imaging overlap with other benign and neoplastic conditions. This pictorial review discusses the intra-abdominal manifestations of this disease on cross-sectional imaging before and after steroid treatment and the main radiological features which help to distinguish it from other key differentials.

Teaching points: • Autoimmune pancreatitis is part of a spectrum of IgG4-related disease. • Diagnosis is based on raised serum IgG4, clinical, radiological and histopathological findings. • Cross-sectional imaging can demonstrate the typical findings of abdominal IgG4-related disease. • Cross-sectional imaging can be used to monitor response to corticosteroid treatment.

Keywords: Autoimmune diseases/diagnosis; Autoimmune pancreatitis; IgG4; Immunoglobulin G.

Fig. 1

Flow chart showing suggested algorithm for distinguishing pancreatic cancer from AIP

Fig. 2

a CECT showing example of diffuse AIP with sausage shaped configuration to the pancreas and subtle peripancreatic halo of low attenuation (arrows). b Axial CECT in a different patient showing example of focal AIP affecting the head of the pancreas (arrows). c Coronal CECT in the same patient (Fig. 2b) demonstrating focal pancreatic head involvement (arrows)

Fig. 3

A patient with a history of mucosa-associated lymphoid tissue (MALT) lymphoma, presenting with raised serum IgG4 and diagnosis of AIP on endoscopic ultrasound (EUS)-guided biopsy. a Axial T2 fat saturated (FS) turbospin echo image shows intermediate to high T2 signal within the pancreas (arrows), but extensive low T2 signal peripancreatic tissue (*). There is diffuse narrowing of the distal pancreatic duct. b Axial T1FS post-contrast arterial phase initially shows reduced enhancement of the peripancreatic tissue (*) compared to the pancreas (arrows). c Axial T1FS post-contrast equilibrium phase showing delayed enhancement of the peripancreatic tissue. d The pancreas and extrapancreatic soft tissue shows marked restricted diffusion with high signal on diffusion-weighted imaging—B800 (arrows), a typical finding in AIP. e The tissue demonstrates corresponding low signal on the ADC map (arrows). f Only the extrapancreatic soft tissue shows high-grade FDG uptake (arrows), a finding which was felt to be atypical for lymphoma

Fig. 4

Axial T1FS post-contrast imaging demonstrating late enhancement in diffuse AIP. a The pancreas is relatively hypointense in the arterial phase (arrows). b The pancreas shows more avid enhancement in the portovenous phase (arrows)

Fig. 5

Coronal FDG-PET/CT study showing multifocal IgG4 disease with involvement of the right lung, tail of the pancreas and retroperitoneum (arrows)

Fig. 6

a Axial T2 balanced gradient echo image shows diffuse enlargement of the body and tail of the pancreas (arrows) with proximal biliary dilatation due to a distal common bile duct (CBD) stricture (*). b Following corticosteroid treatment, the pancreas is less bulky (arrows) and the biliary dilatation is no longer prominent (*) due to resolution of the previous biliary stricture (not shown)

Fig. 7

Example of IgG4 biliary stricture: MRCP shows a long smooth stricture involving the intrapancreatic portion of the CBD (arrow). The proximal pancreatic duct is also attenuated (arrowhead)

Fig. 8

Example of IgG4-related biliary stricture in a different patient. a Strictures are seen in the common hepatic duct and distal CBD (arrows). Sto stomach, Duo duodenum. b ERCP performed 6 months later on the same patient shows resolution of the extrahepatic strictures after treatment with corticosteroids

Fig. 9

Example of IgG4 disease affecting the left kidney. a Axial CECT shows typical wedge-shaped low-density renal cortical lesions in the left kidney (arrows). Both kidneys are stented as there was also IgG4 related retroperitoneal fibrosis. b Coronal FDG PET/CT in same patient as in a showing multifocal high-grade uptake in the left kidney (arrow). c Example of bilateral renal pelvic involvement in a different patient (arrows) on CECT. d Axial T2 turbospin echo image in different patient shows renal lesions (arrows) are of mixed high and low T2 signal (typically reported in the literature as low T2 signal)

Fig. 10

Example of extrarenal IgG4 disease. a CECT showing a rind of abnormal soft tissue (*) anterior to the right kidney and encasing the IVC. b) Axial T2 turbo spin echo image of the same patient as in Fig. 9a shows perirenal soft tissue is of low T2 signal (*). c Axial T1FS pre-contrast shows perirenal soft tissue of intermediate T1 signal (*). d Axial T1FS post-contrast arterial phase shows minimal enhancement of the perirenal soft tissue (*). e Axial T1FS post-contrast equilibrium phase shows delayed enhancement related to a cuff of soft tissue around the IVC (arrow) with most of the perirenal soft tissue remaining low T1 signal (*). f The enhancing tissue around the IVC shows restricted diffusion with high signal on DWI—B800 (arrows). g There is corresponding low signal on the ADC map (arrows)

Fig. 11

Example of IgG4 retroperitoneal fibrosis. a Axial CECT showing enhancing soft tissue partly encasing the IVC and aorta (arrows). b Axial FDG PET/CT showing increased FDG uptake in the abnormal retroperitoneal soft tissue (arrows). c Axial CECT in the same patient, with reduced periaortic soft tissue, following treatment with corticosteroids. d Corresponding T1FS post-contrast MRI showing residual enhancing soft tissue around the aorta following steroid treatment (arrows)