潰瘍性大腸炎関連大腸癌に対するEUSの診断的意義

Value of Endoscopic Ultrasonography in Ulcerative-colitis-associated Colorectal Cancer

要旨　潰瘍性大腸炎関連大腸癌4症例5病変を対象に本症におけるEUSの診断的意義について検討した．浸潤癌の存在診断は内視鏡検査よりもEUSのほうが優っており，1例ではEUS診断が内視鏡診断に先行した．質的診断においては浸潤癌で境界不整な低エコーから癌の診断が可能であり，病変内部にみられる斑状のさらに低エコーの領域は粘液癌に対応した．しかし，粘膜癌やdysplasiaでは炎症による隆起との鑑別はできなかった，深達度診断についても機種を適切に選択すれば良好な診断能が得られると考えられた．またEUSは狭窄や隆起性病変がみられた際に浸潤癌の存在を否定する判断材料でもあった．少数例での検討であり可能性を示唆するにとどまったが，浸潤癌の存在診断を見落とさないためにはサーベイランスにEUSを併用することが有用である可能性がある．

　We attempted to elucidate the value of endoscopic ultrasonography (EUS) in the diagnosis of ulcerativecolitis-associated colorectal cancers based on our experience with five cancers in four cases. The existence of cancer was able to be recognized by EUS in invasive cancers, but mucosal cancers and dysplasias could not be discriminated from inflammatory prominences. In one case, the existence of an invasive cancer was noticed by EUS, preceeding its detection by endoscopy and histological confirmation. The qualitative diagnosis of cancer was possible for invasive cancers by focusing on the hypoechoic area with irregular contour and which was penetrating the wall layers. Also, the presence of mucinous component was discernible in the areas with lower echo level. The depth of cancer infiltration could be estimated by EUS when the instrument was properly chosen. EUS was also useful to exclude the presence of invasive cancers when strictures or prominences were observed. Although the number of cases encountered was small, it seems to us that EUS may have the potential to detect invasive cancers and may be useful if incorporated into cancer surveillance in longstanding ulcerative colitis.