Endoscopic Diagnostics for IgG4-Related Pancreatobiliary Diseases: Current Modalities and Clinical Perspectives

Type 1 autoimmune pancreatitis (AIP), IgG4-related sclerosing cholangitis (IgG4-SC), and IgG4-related cholecystitis are recognized as IgG4-related pancreatobiliary diseases. Endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasonography (EUS) are crucial diagnostic modalities for these conditions. In the diagnosis of AIP, EUS-guided tissue acquisition plays an important role in obtaining histological confirmation and excluding pancreatic cancer (PC). EUS, including contrast-enhanced harmonic imaging and elastography, is used to differentiate focal-type AIP from PC. Endoscopic retrograde pancreatography (ERP) is utilized to obtain a pancreatogram when it is challenging to distinguish AIP from pancreatic cancer. Duodenal papilla biopsy may serve as a supplementary tool, particularly in cases involving the pancreatic head. Cholangiographic classification is essential for differentiating IgG4-SC from PC, primary sclerosing cholangitis (PSC), and cholangiocarcinoma (CCA). ERCP is commonly performed for additional ERCP-related procedures. Intraductal ultrasonography (IDUS) is useful for distinguishing IgG4-SC from CCA or PSC. The primary role of bile duct biopsy is exclusion of malignant biliary strictures; EUS-guided tissue acquisition may also provide histological evidence of IgG4-SC. In the diagnosis of IgG4-related cholecystitis, EUS is helpful to differentiate it from gallbladder cancer. EUS-guided tissue acquisition can aid in confirming IgG4-related cholecystitis and excluding gallbladder cancer or xanthogranulomatous cholecystitis. Transpapillary gallbladder cytology or biopsy may also be considered. Overall, endoscopic modalities play a critical role in diagnosing IgG4-related pancreatobiliary diseases.