indeterminate colitis（広義）の経過

Clinical Course of Indeterminate Colitis

要旨●indeterminate colitis（以下，IC）は，Crohn病と潰瘍性大腸炎の鑑別診断困難例とされてきたが，その概念や定義は時代とともに変遷しつつある．本稿では，まず欧米におけるICの文献的レビューから，ICとinflammatory bowel disease unclassifiedを区別して用いる現状について解説した．さらにICの頻度，経過中の診断確定率，臨床的パターンについて述べ，自施設での経験例を提示した．

　The concept of IC（indeterminate colitis）has changed over the years. Originally, pathologists proposed IC as a diagnosis for colectomy specimens. As per this convention, patients with uncertain diagnosis of CD（Crohn's disease）or UC（ulcerative colitis）but having severe colitis were diagnosed with IC. However, the same terminology was adopted for patients who could not be diagnosed with CD or UC accurately when various factors including clinical, endoscopic, radiographic, and histologic features were considered. In Western countries, the new term“IBDU（inflammatory bowel disease unclassified）”is now used for patients with clinically chronic colitis who clearly have IBD but lack the definitive features of CD or UC. The term“indeterminate colitis”tends to be used for the same condition in Japan, and the definition of IC remains controversial. In this manuscript, we reviewed the literatures regarding IC and IBDU and described the frequency, rates of definite diagnosis, and clinical pattern of IC. The cases with IC that we recently experienced were diagnosed with definite CD in their clinical course. IC is not a definitive entity but a temporary diagnosis, and patients with IC as the first diagnosis need to be carefully followed-up for making the final diagnosis.