X線診断の立場から内視鏡診断に期待するもの―とくに早期胃癌を中心として

What is the Ideal Cooperation between Radiology and Endoscopy in Diagnosis of Early Gastric Cancer ?

はじめに

　近年における胃X線・内視鏡診断技術の進歩は著しく，粘膜面の形態が微細なⅡb様病変や1cmに満たない微小な癌巣までも術前に診断されつつある²⁰⁾²¹⁾．しかし，一方ではルーチン検査で良性病変と診断したものが癌であったり¹⁾，指摘部位とは全く別な部位に新たな癌巣が発見されたり，見逃された癌巣が数年の経過ののちに発見されたりすることも稀ではない．そして，このような症例を集めたretrospectiveな検討を行っても，病変の存在すらわからないものや，病変部の指摘はできたとしても不十分な画像のために性状診断ができないものが多い．ところが，そのいずれにおいても精密検査の段階では，検査の対象となった病変の描出は十分に果たされている．すなわち，精密検査で描出された画像とルーチン検査で描出された画像との差が余りにも大きいことである．ここに画像診断の問題点があり，ルーチン検査のあり方を再検討する必要がある．

　一方，精密検査においては，X線・内視鏡それぞれの分野での高度な技術を駆使した検査・診断が必要であることはいうまでもないが，ルーチン検査では病変の存在を能率よくとらえ，診断していく目的がある．ところで，X線・内視鏡検査の診断能を比較すると，病変の存在部位・形・大きさによってはそれぞれに“強い”面と“弱い”面がある．この点に関しても，現在はX線・内視鏡相互の連携による検査体系のあり方を再検討する時期を迎えているといえるであろう．

　以上のような観点から，本稿ではX線診断の問題点をルーチン検査と精密検査に分けて検討し，内視鏡診断に期待する点を述べてみたい．主に早期胃癌を中心とした検討である．

　Efficacy of routine radiologic examination

　The routine radiologic examination with remote controlled X-ray TV apparatus discovered 88% (161/182) of the early gastric cancer cases, irrespective of their qualitative diagnoses and overlooked 22% (21/182) of them. Of 21 overlooked cases, 6 cases were located at the anterior wall (2 cases at the upper third and 4 cases at the lower third of the stomach) where a drawback of the routine radiologic examination is betrayed most conspicuously. The endoscopy is expected to play an effective role for the discovery of anterior wall lesions.

　Radiologic definition of oral boundary of Ⅱc lesion

　A study was performed as to whether the oral boundary of the Ⅱc lesion could be defined by detailed radiologic examination, based on 84 cases of Type Ⅱc with intramucosal spread from the gastric angle proximally to the lesser curvature. In 27% of them the oral boundary could not be clarified on the double contrast radiographs. At the present time, endoscopic biopsy must be the only method that enables the determination of the oral boundary of the Ⅱc lesions. Especially, carbon ink injection method, combined with aimed biopsy, is considered to be the most reliable procedure that contribute to determine surgical cut line at gastrectomy.

　Radiologic estimation of invasion depth of gastric-carcinoma

　Extent of submucosal involvement is closely related to the deeper involvement of gastric wall, namely that of the proper muscle layer, subserosa and serosa. It was revealed that cancerous infiltration is most probably limited to the submucosal layer if the width of the submucosal involvement is less than 1.0 cm. Further investigation should be directed to quantitative estimation of the extent to the submucosal involvement by endoscopy as well as radiology.

　The diagnosis of microcarcinoma (less than 0.5 cm) and small carcinoma (0.5～1.0 cm)

　The radiologic examination discovered only 16 (12%) of 129 microcarcinomas and 41 (67%) of 61 small carcinomas. The most lesions of the microcarcinomas were discovered as satellite foci by the histologic examination of the resected specimen. An attention should be paid especially to the presence of a microcarcinoma which is located as the satellite focus at the neighboring area of the surgical cut line. The importance of endoscopic observation by the dye-scattering method is appreciated for the discovery of those micro- and small carcinoma.