In tumours reaching the anal canal, or located less than 1 cm from the sphincter, abdomino-perineal resection (APR) is often the only curative surgery which can be realised, with the exception of some small tumours which are conservatively treatable: local excision or proctectomy with intersphincteric resection. In the case of tumours located above 2 cm from the ano-rectal junction, it is almost always possible to preserve the anal sphincter with an onco-logically correct exeresis. In the case of tumours sited between 1 and 2 cm from the anal canal, to achieve a proper distal clearance, we must resort to an inter-sphincteric resection. For tumours whose lower pole is less than 5 cm from the anal verge, a distal resection margin of 2 cm is enough , as long as a com plete exeresis of the mesorectum is performed which caudally ends 2-3 cm from the levator plane.
After Heald et al's basic research on total mesorectal excision (TME) [7, 8] the distal section and anastomosis are performed, therefore, behind the anal canal, making the techniques of low, ultra-low and colo-anal anastomosis more routinary. The colorectal anastomosis is defined as low if the rectal stump is over 2 cm long and ultra-low if it is less than 2 cm. If a total proctectomy with TME is necessary, this will be followed by a manual or mechanic colo-anal anastomosis.
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