大腸多発癌の画像診断―X線診断の立場から

Radiographic Diagnosis of Multiple Cancers of the Large Bowel

要旨　1984年1月から1999年12月までの15年問に当院で発見された大腸多発癌309例を対象に大腸多発癌の臨床的特徴と注腸検査における大腸多発癌診断能の実態について検討を行った．①大腸多発癌の個々の病変は直腸およびS状結腸に多いが病変は広く大腸全体に分布していた．②XP(－)病変の特徴は無茎性病変，10mm以下の病変，右側結腸病変などであった．③第1癌が進行癌の場合，狭窄で口側の検査ができなかったり，前処置不良となり注腸検査の精度が低下し病変が見逃される危険性が高い．また，第1癌発見による油断が異時性大腸多発癌の原因となった症例もみられた．④自験例の同時性2重癌を対象とした大腸検査法の正診率は注腸検査75.3％，内視鏡検査93.3％，併用98.9％であった．注腸検査を大腸多発癌の診断に用いる場合，見逃しの原因をよく理解した上で撮影や読影を行い，疑わしきは積極的に内視鏡検査を併用すべきである．そして，同時性大腸多発癌の見逃しは異時性大腸多発癌の原因となり，発見が遅れると予後に大きな影響を及ぼすので第1癌を発見したら第2癌の存在を念頭に置いた詳細な術前検査と術後の厳重な経過観察が必要である．

　Radiographic diagnosis of multiple cancers of the large bowel was studied over a period of 15 years from 1984 to 1999. It was based on 309 cases. In synchronous cases, the accuracy of preoperative diagnosis was 75.3% by barium enema study alone, and 93.3% by colonoscopy alone, while the rate was 98.9% when colonoscopy and barium-enema study were combined. The cause and problems associated with the lower level of detection by barium enema study were summarized as follows: 1) The most common macroscopic type of missed lesions were nonpedunculated lesions. 2) The lesions were common in the right colon. 3) The size of missed lesions were 10 mm or less. 4) Misjudgment. 5) Malignant obstruction hinders radiographic visualization of the more proximal bowel.

　In order to obtain a more thorough diagnosis when a cancer is first found, careful preoperative examination should be carried out and all patients who have undergone resection of colon cancer should be carefully followed up at short intervals with examination including barium-enema study as well as colonoscopy.