大腸癌見逃し例の検討とその対策

Analysis of Missed Colorectal Cancer and Prevention of Oversight

要旨　当院の初回検査法として行われた注腸X線検査および内視鏡検査によって発見された大腸sm癌，進行癌を対象に，存在診断と見逃し例について検討した．注腸X線検査の見逃し率はsm癌で37％，進行癌で15.4％であった．見逃し例の病変の形態はsm癌ではⅡ型が多かった．進行癌の見逃し例の初回X線像はⅡa型が多く，次いで2型で，それぞれ全体の55％，27％を占めた．部位別にはsm癌では深部結腸に，進行癌では直腸と深部結腸に多かった．見逃しの原因としては読影不十分なものが大半を占めたが，sm癌のⅡ型では病変の指摘が困難なものも多かった．内視鏡検査での見逃し率は8.5％で，見逃し例はⅡa型が多く，上行結腸や直腸のひだの裏側，肝彎曲部や脾彎曲部などの屈曲部にみられた．これらの多くはポリエチレングリコール使用以前のものであった．見逃しの対策は，注腸X線検査では良好な前処置や二重造影，表面型を意識した注意深い読影が重要であり，内視鏡検査では盲点を意識した観察が重要と考えられた．

　The detection and the missed rate of submucosal (sm) and advanced colorectal cancers being initially detected by our barium enema or endoscopic examinations were evaluated. Missed rates of barium enema were 37% for sm cancer and 15.4% for advanced cancer. The most common shape of missed lesions was type Ⅱ in sm cancers. Type Ⅱa (55%) was the leading macroscopic type of missed lesion in the initial x-ray examination, followed by type 2 (27%). As for the location of lesions, the missed sm cancer was common in the right colon and the missed advanced cancer was common in the rectum and right colon. Although improper reading of the film was the major cause of oversight, many type Ⅱ sm cancers were not easy to detect. The missed rate of endoscopic examination was 8.5%, the common shape of missed cancer was type Ⅱa which was located behind the folds in the ascending colon and rectum or at the flexion, particularly at the splenic and hepatic flexion. Oversight was more often prior to the use of polyethylene glycol (PEG) for preparation. For the prevention of oversight, the important points were the appropriate preparation and double contrast technique of barium enema, careful reading of the films with the knowledge of appearance of cancers in the x-ray examination, and the understanding of blind spots of endoscopic examination.