Endoscopic diagnosis of immunoglobulin G4-related sclerosing cholangitis

Abstract

Immunoglobulin G4 (IgG4)-related sclerosing cholangitis (IgG4-SC) is a distinct form of sclerosing cholangitis frequently associated with autoimmune pancreatitis and is recognized as a biliary manifestation of IgG4-related disease. Endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasonography (EUS) are key diagnostic modalities for IgG4-SC. Cholangiocarcinoma and primary sclerosing cholangitis (PSC) are significant mimickers of IgG4-SC. ERCP is employed to evaluate narrowing of the bile duct, with cholangiograms of IgG4-SC classified into four types. This cholangiographic classification is crucial for differential diagnosis. Characteristic cholangiographic findings of IgG4-SC include diffuse or segmental strictures of the intrahepatic or extrahepatic bile ducts and intrahepatic strictures associated with autoimmune pancreatitis. ERCP is particularly useful for differentiating IgG4-SC from PSC because their cholangiographic features differ. EUS and intraductal ultrasonography (IDUS) are used to assess thickening of the bile duct wall. Characteristic IDUS findings in IgG4-SC include circular and symmetrical wall thickening, smooth outer and inner margins, and homogeneous internal echoes at stricture sites. Additionally, bile duct wall thickening at nonstricture sites is a typical IDUS feature of IgG4-SC. Bile duct biopsy is used to evaluate pathological findings, although its diagnostic yield for IgG4-SC is limited; its primary role is to exclude malignant biliary strictures. Duodenal papilla biopsy serves as a supplementary diagnostic tool for IgG4-SC. EUS and tissue acquisition also aid in diagnosing autoimmune pancreatitis as part of other organ involvement. Thus, endoscopic techniques play critical roles in the diagnosis of IgG4-SC.

Keywords: IgG4‐related sclerosing cholangitis; autoimmune pancreatitis; endoscopic retrograde cholangiopancreatography; endoscopic ultrasonography; intraductal ultrasonography.

Figure 1

Cholangiographic classification of immunoglobulin G4‐related sclerosing cholangitis. Adapted from Ohara et al. 2012, with permission from John Wiley and Sons. Type 1: Stenosis is confined to the lower common bile duct. Type 2: Stenosis is diffusely distributed throughout the intrahepatic and extrahepatic bile ducts. Type 2a: Stricture of the intrahepatic bile ducts with prestenotic dilation. Type 2b: Stricture of the intrahepatic bile ducts without prestenotic dilation and with reduced bile duct branches. Type 3: Stenosis involves both the hilar hepatic and lower common bile ducts. Type 4: Stenosis is limited to the hilar hepatic bile ducts. Arrows indicate stenosis of the bile ducts.

Figure 2

The characteristic features of cholangiograms between immunoglobulin G4‐related sclerosing cholangitis (IgG4‐SC) and primary sclerosing cholangitis (PSC) on endoscopic retrograde cholangiography. Adapted from Ohara et al. 2012, with permission from John Wiley and Sons.

Figure 3

Intraductal ultrasonography (IDUS) findings of immunoglobulin G4 (IgG4)‐related sclerosing cholangitis (IgG4‐SC). Endoscopic retrograde cholangiography showing intrapancreatic strictures. (a) IDUS reveals wall thickening in the intrapancreatic stricture. IDUS findings include circular‐symmetrical wall thickening with smooth inner and outer margins. (b) IDUS demonstrates wall thickening in the middle bile duct at a nonstricture site. (c) IDUS shows wall thickening in the hilar bile duct at a nonstricture site.

Figure 4

Intraductal ultrasonographic findings in the biliary stricture among immunoglobulin G4‐related sclerosing cholangitis (IgG4‐SC), primary sclerosing cholangitis (PSC), and cholangiocarcinoma (CCA).

Figure 5

Peroral cholangioscopy (POCS) findings of immunoglobulin G4 (IgG4)‐related sclerosing cholangitis (IgG4‐SC). Images courtesy of Dr. Yasutaka Ishii, Hiroshima University. Endoscopic retrograde cholangiography showing intrahepatic and hilar strictures before steroid therapy. POCS reveals a smooth mucosal surface, dilated vessels without caliber alteration, and an absence of easy bleeding in (a) white light imaging and (b) in narrow‐band imaging before steroid therapy. (c) Biliary stricture and dilated vessels are improved after steroid therapy in white light imaging.

Figure 6

The algorithm for the endoscopic diagnosis of immunoglobulin G4 (IgG4)‐related sclerosing cholangitis (IgG4‐SC). AIP, autoimmune pancreatitis; Bx, biopsy; CT, computed tomography; ERCP, endoscopic retrograde cholangiopancreatography; EUS, endoscopic ultrasonography; EUS‐TA, EUS‐guided tissue acquisition; IDUS, intraductal ultrasonography; MRCP, magnetic resonance cholangiopancreatograpy; MRI, magnetic resonance imaging; POCS, peroral cholangioscopy; US, ultrasonography.