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要旨 肛門管の上縁は恥骨直腸筋の上縁,すなわち歯状線の上方に位置する6~12mmの移行上皮部の境界であるHerrmann線に一致する.側方発育傾向を有するLSTは,しばしば,直腸(Rb)から移行上皮部分に進展し,歯状線に接する.以上のうち,推定深達度MやSM浅層にとどまる病変は局所一括切除であるESDの適応となる.したがって,歯状線に接する病変に対するESDの適応は,原則として,大腸ESD標準化検討部会の提唱する基準と同様で,内視鏡的一括切除が必要な病変のうち,(1)スネアによる一括切除が困難な,LST-NG,特にpseudo-depressed type,Vi型pit patternを呈する病変,SM軽度浸潤癌,大きな陥凹型腫瘍,癌が疑われる大きな隆起性病変,(2)粘膜下層に線維化を伴う粘膜内病変,(3)潰瘍性大腸炎などの慢性炎症を背景としたsporadicな局在腫瘍,(4)内視鏡的切除後の局所遺残再発早期癌である.一方,ESD術後に肛門狭窄が危惧される亜全周から全周性の病変は相対的適応と判断され,狭窄対策が課題である.歯状線に接するESD症例を12例経験したが,大きさ平均は46.4mmで遺残再発や偶発症は認めていない.本手技では,知覚神経を有する歯状線部分において局所麻酔剤を用いた疼痛対策が必要となる.また,剝離では移行上皮部の粘膜下層の内痔静脈層,ならびに上直腸動脈の肛門枝の止血操作を確実に行うことが重要となる.一方,ESDは従来から施行されてきたTARと比較して局所再発をほとんど認めないこと,診断から治療の一連の流れの中で行いうる低侵襲の治療であることなどの点で優れており,今後歯状線に接する病変の治療において重要な役割を担うと思われた.
Patients suffering from colorectal cancers have markedly increased by 2.5 times among recent 20 years in Japan. The progress of the endoscopic resection techniques such as ESD(endoscopic submucosal dissection)has led to changes in therapeutic strategies for early colorectal cancers. Also the ESD technique is a very useful endoscopic procedure, making it possible to perform en bloc resection of rectal tumors advancing to the anal canal. ESD was performed for 442 cases of colorectal neoplasms in 430 patients(male : female=260 : 170 ; mean age, 66.8 years). Among these cases, 12 cases were located in the rectum to the anal canal close to the dentate line. The average size of the tumors was 46.4mm in diameter.
Indication for ESD for rectal neoplasms advancing to the anal canal was thought to be the same as the criteria proposed by The Colorectal ESD Standardization Implementation Working Group. The indications were as follows, (1)Lesions that were larger than 20 mm in diameter in which en bloc resection using snare EMR is difficult, (2)Mucosal lesions with fibrosis caused by prolapse due to biopsy or peristalsis of the lesions, (3)Sporadic localized tumors with chronic inflammation such as ulcerative colitis, (4)Local residual early cancer after endoscopic resection. It should be added that en bloc resection using the ESD procedure for circumferential-type tumors is considered to be a conditional indication due to the risk of anal stenosis.
On the other hand, the incidence of local recurrence with TAR was reported to be high(12 to 30%). However, local recurrence and severe complications related to ESD were not observed in our series. Because of above mentioned reasons, ESD seems to play an important role in the therapeutic strategy for treating rectal tumors advancing to the anal canal.
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