Intersphincteric resection for very low rectal cancer
Goals for rectal cancer surgery include complete tumor resection to minimize the risk of relapse and maintenance of quality of life. Local control and survival of patients with rectal cancer have improved with the development of surgical techniques and co
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Introduction Goals for rectal cancer surgery include complete tumor resection to minimize the risk of relapse and maintenance of quality of life. Local control and survival of patients with rectal cancer have improved with the development of surgical techniques and combined adjuvant therapy. The advent of double-stapling techniques and coloanal anastomosis has facilitated the construction of very low rectal anastomosis. Historically and practically, decision-making is related to the distance from the lower edge of tumor to the anal canal. This is because of the potential risk of both intramural and mesorectal microscopic spread below the tumor. Therefore, at least 5 cm of distal margin was required until the 1980s [1], after which 2 cm was considered adequate [2]. In fact, it is not technically possible to obtain a 2 cm distal margin by using conventional abdominal approach in patients with rectal tumors located below 5 cm from the anal verge, because the median length of the anal canal is 3 to 4 cm. Furthermore, to obtain an adequate radial margin with sphincter preservation in very low rectal cancer is not certain. Therefore, for both technical and oncological reasons, it is generally accepted that most rectal cancers less than 5 cm from the anal verge (AV) or less than 2 cm from the dentate line (DL) are treated by using abdomino-perineal resection (APR). However, recent studies have shown that a margin of more than 2 cm is not necessary to prevent local recurrences, and a distal margin of 1 to 2 cm is now considered sufficient in most instances, with local recurrence rates of 4 to 13 percent [3–5]. Considering the above-mentioned background, intersphincteric resection (ISR) with coloanal anastomosis has been proposed to avoid permanent colostomy for rectal
cancers located less than 5 cm for the AV by a few specialized teams [5–7]. The goal of ISR is to divide the rectum transanally and to remove part or the whole of the internal anal sphincter, to obtain both adequate distal and radial margin in order to prevent a permanent colostomy. A more modern concept focuses on the radial margin more than the distal margin [6, 8, 9]. In other words ISR can be an alternative to APR for selected rectal tumors situated at the anorectal junction, without compromising oncological outcomes.
Anatomy of the anal canal (Fig. 1) It is obligatory to know the anal anatomy very well in order to carry out ISR precisely. The surgical anal canal can be defined as the distance between the anorectal ring and the AV. The intersphincteric groove can be palpable as a little hollow by careful digital examination. The cranial portion of intersphincteric groove becomes narrow and cylindrical with a length of 3 to 4 cm. After passing this narrow portion, the upper edge of anorectal ring, which is defined by the sling of muscle forming the anal hiatus of the pelvic diaphragm can be palpated. The anorectal ring is corresponding to the superior margin of puborectalis muscle attachment. It is called alias Herrmann’s line. The mesorectum is thin or lac
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