NBIによる大腸表面型腫瘍のスクリーニング

Screening for Superficial Colorectal Tumor Using Narrow Band Imaging

要旨●大腸表面型腫瘍のスクリーニングは，内視鏡機器の進化とともに白色光（white light imaging ; WLI）からNBIなどの画像強調観察へと変わりつつある．当院でのWLIとNBIによる腫瘍発見能の比較検討では，NBIがLST-NGの発見に有用であった．また，陥凹型腫瘍のNBI所見は，陥凹面が白色調，反応性隆起部はbrownish areaとして視認され，これを“O-ring sign”と呼び，NBIによる陥凹型腫瘍発見の特徴像と考えられた．なお，盲腸に限局してWLI→NBI→インジゴカルミン色素（chromoendoscopy ; CE）の順に観察をし，微小腺腫の発見数を前向きに検討したところ，CE 47病変>NBI 37病変>WLI 11病変で，最終観察のCE観察で発見された微小腺腫が最多であり，CE観察がそのほかと比較して最も有用であった．現状の全大腸スクリーニングには，NBI観察による盲腸からの抜去観察が有用だが，将来へはCE観察を越える画像強調観察への開発が期待される．

　Screening for superficial colorectal tumors has evolved over time with advances in endoscopic technology ; conventional WLI（white-light imaging）is being increasingly replaced with IEE（image-enhanced endoscopy）with NBI（narrow-band imaging）as the mainstay for screening. Of note, a comparison between WLI and NBI has shown the superiority of NBI over WLI in detecting non-granular type（LST-NG）tumors. Depressed and reactive elevated areas of depressed tumors are visualized as whitish and brownish areas, respectively, on performing NBI, which together constitute the so-called“O-ring sign”that is characteristic of the NBI findings of depressed tumors. Prospective screening for cecal diminutive adenomas alone sequentially with WLI, NBI, and chromoendoscopy（indigo carmine dye spraying）has shown that cecal diminutive adenomas are most frequently detected with chromoendoscopy, followed by NBI and WLI（47, 37, and 11 lesions, respectively）, suggesting the usefulness of chromoendoscopy. Thus, while NBI appears to represent the mainstay for pan-colonic screening at present, further refinements in IEE are required to improve chromoendoscopy in pan-colonic screening.