大腸壁在癌の存在診断

Radiological and Endoscopic Screening of Colonic Cancer

要旨　大腸sm癌，pm癌とss（a₁）癌を対象にして存在診断に関する検討を行った．sm癌，pm癌の25％は無症状であった．sm癌の約半数は免疫便潜血検査が陰性であり，陽性例の病変最大径は陰性例に比し有意に大きかった．X線検査によるsm癌の存在診断率は初回X線検査群（16例）では62.5％であったが，精密X線検査群（51例）では100％であった．一方，内視鏡検査による存在診断率は初回検査および繰り返し内視鏡検査ともに100％であった．pm癌17例とss（a₁）癌55例ではそれぞれ1例ずつX線検査による存在診断不能例があり，全体の初回X線検査存在診断率は88例中80例90.9％であった．X線検査によって存在診断が不可能であった原因は，①読影時の見落とし（8例中6例），②バリウムの付着不良（4例），③右側結腸病変の見落とし（8例中6例）が主であった．以上より，大腸癌存在診断能を向上させるためには，右側結腸の丁寧な検査とX線読影能の向上，前処置の改善が必要で，また全大腸内視鏡検査を頻用することが望ましいと結論した．

　This study was undertaken to evaluate the accuracy of radiological and endoscopic diagnosis of colonic cancer with submucosal (sm), proper muscle (pm) and subserosal invasion (ss). Twenty five percent of patients having cancer with submucosal and proper muscle invasion did not have symptoms. A half of the patients having cancer with submucosal invasion showed negative immunological fecal occult blood test (FOBT). The average diameter of the sm cancer with positive FOBT was significantly larger than that of sm cancer with negative FOBT (p＜0.05).

　Examination by radiological screening detected 10 of 16 cancers (62.5%) with sm invasion. However, reexamination visualized all of 51 lesions with sm invasion. Three quarters of the lesions undetected by screening radiography were located at the right side of the colon, mostly at the cecum. In contrast, screening endoscopic examination detected all the 16 cancers with sm invasion. 98.2% of ss cancers, and 94.1% of pm cancers were able to be detected by radiological screening. The main reason for diagnostic inaccuracy of radiography seemed to be the difficulty in detecting flat tumors on films of the cecum. Therefore, to improve the diagnostic accuracy of radiological screening, it seems that it is very important to check by improved radiographic techniques and thorough colonoscopic examination whether or not there are subtle easily-missed lesions in the cecum.