早期大腸癌深達度診断における拡大内視鏡と超音波内視鏡の役割

Effectiveness of Magnifying Endoscopy and Endoscopic Ultrasonography in Diagnosing Invasion Depth of Early Colorectal Cancer

要旨　早期大腸癌深達度診断における拡大内視鏡と超音波内視鏡（EUS）の有用性を明らかにすることを目的として通常内視鏡と比較した深達度診断能の検討を行い以下の結果を得た．①診断不能病変を含めたsm_2～3の診断能は感度，特異度，正診率ともに通常内視鏡が拡大内視鏡，EUSより高かった．②拡大内視鏡によるsm_2～3の診断能は他の検査に比べ感度が極端に低かった．診断能向上のためにはV_Ⅰpitの亜分類が必要と考えられた．しかし，V型以外のpitにはSM2～3は存在しなかった．③EUSの診断不能率は最も高かったが，診断不能病変を除いたsm_2～3の診断能は通常内視鏡に近かった．また，通常内視鏡で誤診した6病変のうち3病変を正診していた．以上をまとめると，通常内視鏡が最も診断能の高い優れた検査法である．しかし，それのみでは十分診断できない病変も存在し，通常内視鏡による深達度診断に確信が持てない病変に対しては積極的に他の検査，特にEUSを施行すべきである．

　A comparative study on conventional, magnifying endoscopy and endoscopic ultrasonography was carried out to clarify the effectiveness of magnifying endoscopy and endoscopic ultrasonography in the diagnosis of invasion depth of early colorectal cancer.

　The following results were obtained : 　1. Diagnostic accuracy by conventional endoscopy of sm_2～3 cancer was greater than that by magnifying endoscopy or endoscopic ultrasonography.

　2. Diagnostic sensitivity of magnifying endoscopy was remarkably low. To make up for this, attention to the subclassification of type V_Ⅰ pit pattern seemed to be mandatory. sm_2～3 cancer was never found with pit patterns other than type Ⅵ or type Ⅴ.

　3. Endoscopic ultrasonography was least able to detect the presence of early cancers, but its ability to diagnose lesions which it could detect was similar that of conventional endoscopy. Moreover, it diagnosed correctly 3 of the 6 lesions which were diagnosed mistakenly by conventional endoscopy.

　In summary, while conventional endoscopy showed the highest detection ability, there were lesions that were incorrectly diagnosed by conventional endoscopy alone. Thus, when the depth of invasion can't be diagnosed confidently by conventional endoscopy alone, the use of endoscopic ultrasonography in particular is recommended as a back-up to conventional endoscopy.