大腸憩室疾患の病理

The Pathology of Diverticular Disease

要旨　大腸憩室および大腸憩室に関連した疾患・病変について概説した．本稿で取り扱った項目は，大腸憩室の臨床病理学的基礎事項，憩室炎・憩室周囲炎，虫垂憩室炎，憩室炎の合併症，MPS様の炎症性隆起性病変，およびdiverticular colitisである．MPS様の隆起性病変は，憩室症に伴う腸管の短縮・拡張不良によって憩室周辺に生じた“たるんだ”粘膜が慢性的な牽引性の機械的刺激を受けることにより形成される．diverticular colitisとは大腸憩室症に時に合併する区域性の慢性腸炎で，内視鏡的にも組織学的にもIBD，特に潰瘍性大腸炎に類似した所見を呈する．生検組織所見のみではdiverticular colitisと潰瘍性大腸炎の鑑別が困難な例も存在する．両者の鑑別で重要な点は，diverticular colitisでは肉眼的（内視鏡的）にも，組織学的にも直腸に炎症所見が乏しいことである（rectal sparing）．

　Clinicopathologic features of diverticular disease and lesions associated with diverticular disease were outlined. We described the clinicopathological basis of the diverticular disease, diverticulitis・peridiverticulitis, diverticulum of the appendix, complications of diverticulitis, mucosal prolapse syndrome（MPS）-like inflammatory lesion associated with diverticular disease, and diverticular colitis. In shortened thick-walled segments of the bowel with diverticulosis, the redundant mucosa is forced characteristically into polypoid folds, which are MPS-like inflammatory lesion associated with diverticular disease. Diverticular colitis is a chronic inflammatory condition associated with diverticular disease, and is similar in both endoscopic appearance and histopathological feature to the colonic mucosa in inflammatory bowel disease. It is sometimes difiicult to distinguish diverticular colitis from ulcerative colitis by only the histopathological feature of the endoscopic biopsy specimen. Critically important in these cases is the morphology of the rectal mucosa : if it is complicated by an inflammatory process the diagnosis is inflammatory bowel disease, suggestive of ulcerative colitis.