潰瘍性大腸炎・Crohn病の鑑別診断における生検の役割―病理の立場から

Usefulness of Colorectal Biopsy in Differential Diagnosis of Ulcerative Colitis and Crohn's Disease

要旨　潰瘍性大腸炎（UC）とCrohn病（CD）は，最近の診断基準の進歩により，積極的かつ客観的に生検診断できるようになった．診断は，第一段階で特発性炎症性腸疾患（IBD）とIBD以外の大腸炎（non-IBD）を，第二段階でUCとCDを鑑別する方法に従うのが最も実際的である．IBDとnon-IBDの診断基準の精度は一般に高く，97％を超えるものがある一方で，UCとCDについては感度と特異度を両立させることが困難であった．しかし，組織所見の大腸内分布を反映させた新たな診断基準では，実用的レベルの感度（89～94％）と特異度（97％以上）を達成している．病理診断に寄与できる質の高い生検を採取するために，内視鏡医も診断基準の内容を十分把握しておく必要があろう．

　Colorectal biopsy is useful in the diagnosing of patients with colitis, in whom it is most important to make a differential diagnosis between idiopathic inflammatory bowel disease (IBD) and other forms of colitis (non-IBD) and between ulcerative colitis (UC and Crohn's disease (CD). Sometimes this diagnosis is controversial. Published criteria for IBD and non-IBD had a high diagnostic validity exceeding 97%, but high sensitivity and specificity were incompatible in differentiating between UC and CD. This difficulty was recently overcome by using histological features representing a colorectal distribution of the underlying disease. New criteria for UC and CD enabled high specificity exceeding 97%, and their sensitivities were 89% and 94%, respectively. More accurate biopsy diagnosis is now possible, and endoscopists need to understand the content of the criteria in order to take biopsy specimens appropriately.