見落とし大腸癌の検討―注腸造影検査と大腸内視鏡検査を主体に

Study of Colorectal Cancers Overlooked in Barium Enema Examination and Colonoscopy

要旨　1986年以来当科で経験した大腸進行癌525例とsm癌75例を対象に注腸造影検査と大腸内視鏡検査の見逃しにつき検討した．注腸造影によるsm癌と進行癌の見逃し率は，各々6.7％，1.6％であった．見逃しの多い部位は上行結腸とS状結腸であり，造影不十分と腸管の重なりが大きな原因となっていた．上行結腸では圧迫を加えた撮影が大切である．大腸内視鏡検査の見逃しは0.6％あり，全腸管を観察していないことが原因であった．内視鏡で経過観察中発見されたsm癌4例中3例は，Ⅱa＋Ⅱc型の表面型癌であり，特にS状結腸で発見の頻度が高い．注腸造影検査，大腸内視鏡検査において早期癌のみならず進行癌の見逃しも皆無ではなく，十分考慮し日常診療を行うことが大切である．

　We analyzed the factors involved in colorectal cancers overlooked in barium enema examination and colonoscopy. Five hundred and twenty five advanced cancers and 75 sm cancers were analyzed retrospectively with respect to their diagnostic processes.

　The miss rate of sm cancers by barium enema study was 6.7% in all patients, and it was showed that 1.6% of all advanced cancer cases were missed by barium enema study. The site where these cancers were overlooked most frequently was the ascending colon and the sigmoid colon, and the factors involved were incomplete examination or overlapping with the colon. The compression maneuver was very useful in helping to avoid missing the cancerous lesions in the ascending colon. The miss rate of advanced cancer by colonoscopy was 0.6%. Colonoscopic misses resulted from incomplete investigation. Three out of 4 sm cancers which were detected during follow-up colonoscopy were Ⅱa＋Ⅱc type. Cancers undetected by colonoscopy were found frequently in the sigmoid colon.

　In conclusion, it can be said that the number of sm cancers and advanced colorectal cancers undetected by either barium enema or colonoscopy is by no means small, and every effort should be exerted to eliminate these misses.