炎症性腸疾患と腸管感染症

Inflammatory Bowel Disease and Infectious Enterocolitis

潰瘍性大腸炎（UC）ではカンピロバクター腸炎，サルモネラ腸炎，アメーバ性大腸炎との鑑別が重要である．これらの感染性腸炎との鑑別では，内視鏡的鑑別診断に加えて詳しい問診が重要であり，必ず便培養検査を行う．Crohn病（CD）ではエルシニア腸炎や腸結核との鑑別が重要である．腸結核とCDの鑑別では，内視鏡所見に加えクォンティフェロン検査や胸部CT検査が補助診断として重要である．炎症性腸疾患（IBD）の増悪因子としてClostridium difficile（C. difficile）感染症とサイトメガロウイルス（CMV）感染症の合併が問題となっている．IBDに合併したC. difficile感染症は増悪因子のみではなく予後不良の因子である．IBDでは偽膜形成することが少なく内視鏡像で診断することが難しい．UCに合併したCMV感染症はUCの重症化や難治化に関与している．内視鏡像は重症UCの像とほぼ同じであり，内視鏡像のみでの診断は難しいため，CMV抗原測定，組織学的検査，粘膜CMV-DNA検査などを行う．

　Infectious cases of enterocolitis which need differential diagnosis from UC（ulcerative colitis）include Campylobacter enterocolitis, Salmonella enterocolitis and amebic colitis. For correct diagnosis, in addition to colonoscopic findings, detailed questioning and fecal culture are useful. Infectious cases of enterocolitis which need differential diagnosis from CD（Crohn's disease）include Yersinia enterocolitis and intestinal tuberculosis. For differential diagnosis between CD and intestinal tuberculosis, in addition to colonoscopic findings, chest computed tomography and the QuantiFERON TB-2G test are useful.

　In recent years, C. difficile（Clostridium difficile）and CMV（cytomegalovirus）have become recognized as risk factors for exacerbation of inflammatory bowel disease. C. difficile infection with IBD（inflammatory bowel disease）is not only a risk factor for exacerbation, but also a risk factor for poor prognosis. Typical evidence of colonic changes with C. difficile infection, including pseudomembranous exudate, is often not present. CMV infection with UC plays an important role in exacerbation and refractory progress of UC. To diagnose CMV infection with UC, not only colonoscopic findings, but also CMV antigenemia, histology including immunohistochemistry and mucosal polymerase chain reaction for the CMV genome are useful.