腹部：実質臓器（肝胆膵脾）

Imaging findings of autoimmune disorders（hepatobiliary system, pancreas, spleen）

自己免疫疾患の範疇に含まれる疾患は数多く存在し，肝胆膵領域にも多彩な病変を引き起こす。これらの臓器における自己免疫疾患は早期診断と適切な治療介入が重要であり，画像診断は疾患の特徴をとらえ，病態を正確に評価するうえで不可欠な役割を果たす。本稿では，肝臓における代表的な自己免疫疾患として自己免疫性肝疾患，胆膵における代表的な自己免疫疾患としてIgG4関連疾患を取り上げる。また，最近遭遇する頻度が増えてきた免疫関連有害事象（immune related adverse events：irAE）についても肝胆膵領域の画像所見を概説する。

Autoimmune diseases can affect the hepatobiliary and pancreatic systems, requiring early diagnosis and appropriate treatment. Imaging plays a crucial role in characterizing these diseases and assessing their progression. This article focuses on autoimmune liver diseases and IgG4-related diseases affecting the biliary and pancreatic systems. Additionally, immune-related adverse events（irAE）, increasingly encountered due to immune checkpoint inhibitors, are discussed. While CT and MRI are essential for diagnosis, many findings are non-specific. Recognizing characteristic imaging features is important, and considering patient history and treatment course is necessary for accurate interpretation, especially as irAE cases continue to rise.