直腸肛門部の内視鏡・EUS診断

Diagnosis of Disorders in the Anorectal Region by Colonoscopy and EUS

要旨　直腸肛門部は内視鏡の挿入が容易である一方で観察盲点が多い．下部直腸から肛門管の十分な観察には直腸内反転が有用である．解剖学的にみて，この領域は上皮の構成が複雑であり，様々な周囲臓器が存在し，血管支配も他の領域と異なっている．さらに直腸肛門部は排便機能を司る領域であるのみならず，性行為による感染源の侵入経路，薬剤の投与経路でもある．これらの理由で直腸肛門部は大腸の他の領域と比べて疾患発生の上で特異な場を形成している．したがって多彩な疾患構成を熟知した上で検査を行う必要がある．EUSを用いることによって腸管壁の層構造や壁外の情報を得ることができる．腫瘍性疾患においては病変の局在，組織像の推定に，炎症性疾患においては炎症の程度や波及範囲を知るとともに病理学的変化を理解する上で有用である．

　The complete observation of the anorectal region is difficult, although the insertion of an endoscope through this area is easy. The retroversion of a scope in the rectum is very useful for the observation of the lowermost portion of the rectum and the proximal anal canal. Anatomically, this region is characterized by diverse epithelial components, surrounding organs, and blood supply. This area plays an important role in defecation. At the same time, it becomes the entrance of sexually transmitted pathogens and a route for drug administration. For these reasons, this area in a unique location in disease development. Accordingly, the knowledge of disorders in this region is indispensable for examiners. EUS can visualize the layered structure of the intestinal wall as well as produce images of the outside. In the evaluation of tumor, EUS can afford the information of its localization and suggestions concerning its histological type. In the evaluation of inflammation, information concerning its degree, extent, and histological events can also be obtained by EUS.