内藤 格, 中沢 貴宏

Itaru NAITOH, Takahiro NAKAZAWA

名古屋市立大学大学院医学研究科消化器・代謝内科学

Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences

キーワード : autoimmune pancreatitis, endoscopic retrograde cholangiopancreatography, IgG4-related disease, IgG4-related sclerosing cholangitis, intraductal ultrasonography

自己免疫性膵炎（autoimmune pancreatitis: AIP）における主膵管狭細像やIgG4関連硬化性胆管炎（IgG4-related sclerosing cholangitis: IgG4-SC）における胆管狭窄の評価には内視鏡的逆行性胆管膵管造影が用いられている．また，胆管腔内超音波検査は，IgG4-SCにおける胆管壁肥厚の詳細な評価に有用である．膵癌，胆管癌，原発性硬化性胆管炎は，AIPやIgG4-SCと鑑別すべき重要な疾患である．著名な上流拡張を伴わないびまん性または限局性の膵管狭細像は，AIPに特徴的な膵管造影所見である．一方，上流拡張が著名な単発の距離の短い膵管狭窄像は，膵癌に特徴的な所見である．IgG4-SCの胆管像は胆管狭窄部位により4つのタイプに分類され，この胆管像分類はIgG4-SCの鑑別診断において重要である．内視鏡的逆行性胆管膵管造影は，IgG4-SCと原発性硬化性胆管炎の鑑別診断に有用である．距離の長い胆管狭窄や膵内胆管狭窄はIgG4-SCに特徴的な所見であるのに対し，帯状狭窄，数珠状あるいは剪定状所見，憩室様突出は，原発性硬化性胆管炎に特徴的である．胆管狭窄部における全周性で対称性な胆管壁肥厚，滑らかな外側縁や内側縁，均一な内部エコーは，IgG4-SCに特徴的な胆管腔内超音波所見であり，IgG4-SCの診断に有用である．胆管非狭窄部位における胆管壁肥厚もIgG4-SCに典型的な胆管腔内超音波所見であり，胆管癌との鑑別診断において重要である．内視鏡的逆行性胆管膵管造影に引き続き施行可能な経乳頭的胆管生検や十二指腸乳頭部生検もIgG4-SCの診断において有用である．

Endoscopic retrograde cholangiopancreatography is used to evaluate the narrowing of the main pancreatic duct in autoimmune pancreatitis (AIP) and biliary stricture in IgG4-related sclerosing cholangitis (IgG4-SC). Intraductal ultrasonography enables detailed visualization of the thickening of the bile duct wall in IgG4-SC. Pancreatic cancer, cholangiocarcinoma, and primary sclerosing cholangitis are important mimicking conditions of AIP and IgG4-SC. Diffuse or segmental stricture without marked upstream dilatation is a typical pancreatographic finding in AIP. By contrast, a single, short stricture with marked upstream dilatation is a typical finding in pancreatic cancer. The cholangiogram of IgG4-SC is classified into four types based on biliary stricture location, and this cholangiogram classification is useful for the differential diagnosis of IgG4-SC. Endoscopic retrograde cholangiography can be used to distinguish between IgG4-SC and primary sclerosing cholangitis. A segmental/long and intrapancreatic stricture is a characteristic finding of IgG4-SC, whereas band-like strictures, a beaded or pruned-tree appearance, and diverticulum-like outpouching are characteristic of primary sclerosing cholangitis. The characteristic intraductal ultrasonographic findings of circular・symmetrical wall thickening, smooth outer and inner margins, and homogeneous internal echo at the biliary stricture site are useful for diagnosis of IgG4-SC. Thickening of the bile duct wall at non-stricture sites is also a typical intraductal ultrasonographic finding of IgG4-SC and can be used for differential diagnosis from cholangiocarcinoma. Transpapillary bile duct and duodenal papilla biopsy during endoscopic retrograde cholangiopancreatography are also useful in the diagnosis of IgG4-SC.