Autoimmune (IgG4) Cholangitis

Published on 19/07/2015 by admin

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Last modified 19/07/2015

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 Strictures long and smooth without irregularity and may cause proximal biliary dilatation

• MR: MRCP images nicely demonstrate irregularity and strictures of intrahepatic or extrahepatic bile ducts (most commonly affecting distal CBD)

image Affected segments demonstrate concentric ductal wall thickening with hyperenhancement on T1WI C+
image Stricture long and smooth (without irregularity)
image Findings of concomitant autoimmune pancreatitis

– Enlarged pancreas with abnormal signal (hypointense on T1WI and hyperintense on T2WI)
– Rim of peripheral hypoenhancement and low T2WI signal with delayed enhancement
– Multiple discontiguous pancreatic duct strictures on MRCP, which may resolve after administration of secretin
• CT: Circumferential focal or diffuse bile duct wall thickening with hyperenhancement of affected segments

PATHOLOGY

• Frequently associated with imaging findings of autoimmune pancreatitis and other manifestations of IgG4-related sclerosing disease
• Exact pathophysiology not well understood, but some evidence for both autoimmune and allergic mechanisms

CLINICAL ISSUES

• Typically affects middle-aged and elderly males
• Diagnosis based on a combination of imaging, histopathology, serologic (↑ IgG4) markers and clinical response to steroids/azathioprine
• May improve spontaneously, progress, or relapse, although relapse rate after therapy may be high (> 50%)
• Treatment with steroids typically effective, although other immunomodulators utilized in refractory cases
image
(Left) CECT of a jaundiced patient shows a thickened, slightly dilated common bile duct (CBD) image and an enlarged, sausage-shaped pancreas image. The appearance of the pancreas is consistent with autoimmune pancreatitis (AIP), and an elevated IgG4 indicates that the bile duct thickening is due to IgG4-related sclerosing cholangitis (ISC).

image
(Right) ERCP in same patient shows a stricture image of the distal CBD, the most common manifestation of ISC. ISC and AIP resolved after steroid and azathioprine therapy.
image
(Left) Coronal CECT in a patient with known autoimmune pancreatitis (not shown) demonstrates tapered narrowing of the distal CBD image with wall hyperenhancement, compatible with autoimmune cholangitis.

image
(Right) Coronal CECT in a patient with known autoimmune pancreatitis demonstrates wall thickening, hyperenhancement, and narrowing of the CBD image with proximal biliary dilatation image, in keeping with IgG4-related cholangitis.

TERMINOLOGY

Synonyms

• IgG4-related sclerosing disease (IRSD), IgG4-related sclerosing cholangitis (ISC)

Definitions

• IRSD: Spectrum of disorders characterized by tumor-like lymphoplasmacytic infiltration and varying degrees of fibrosis in different organs

image Pancreas is most commonly affected organ (autoimmune pancreatitis) followed by salivary glands and biliary tree
• ISC: Biliary manifestations of IRSD frequently associated with autoimmune pancreatitis (AIP)

image Manifested as wall thickening and biliary strictures

IMAGING

General Features

• Best diagnostic clue

image Bile duct wall thickening and strictures in setting of autoimmune pancreatitis
• Location

image ISC classified based upon stricture location

– Type 1: Distal (intrapancreatic) common bile duct (CBD)

image Most common type: May mimic pancreatic adenocarcinoma or cholangiocarcinoma
– Type 2: Strictures distributed throughout intra- and extrahepatic ducts

image May mimic primary sclerosing cholangitis
– Type 3: Strictures of duct bifurcation and distal duct

image May mimic cholangiocarcinoma
– Type 4: Isolated hilar stricture

image May mimic cholangiocarcinoma
• Size

image Variable: Focal or diffuse involvement of biliary tree
• Morphology

image Concentric bile duct wall thickening and hyperenhancement
image Typically long smooth stricture with upstream biliary ductal dilatation

Radiographic Findings

• ERCP

image Distal CBD stricture and irregularity of main pancreatic duct (due to concomitant AIP) most frequent findings
image Strictures of intra- and extrahepatic ducts rarely occur without pancreatic duct involvement
image Long, smooth strictures (particularly of distal CBD) without irregularity

CT Findings

• Circumferential focal or diffuse bile duct wall thickening

image Most commonly affects distal CBD, but can affect any portion of biliary tree
image Hyperenhancement of affected bile duct: Enhancement may persist during delayed phase
image No vascular invasion, metastatic disease, or other secondary findings of malignancy
• No clear association between ISC and malignancy, but involved sites in biliary tree may rarely appear mass-like and mimic malignancy (inflammatory pseudotumor)
• Diffuse gallbladder wall thickening (due to either lymphoplasmacytic infiltration and transmural fibrosis or superimposed cholecystitis)
• Findings of concomitant autoimmune pancreatitis

image Focal, multifocal, or diffuse (sausage-shaped) pancreatic enlargement with hypodense pancreatic capsule
image Enlargement of pancreas with a paucity of peripancreatic inflammation, fluid, or stranding
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