Accurate understanding of the pelvic anatomy is critical to achieving good oncological and functional outcomes after rectal excision. Heald et al. (1998) in Basingstoke introduced the concept of total mesorectal excision during the 1980s. Total Mesorectal Excision (TME) consists of separate high ligation of the inferior mesenteric vessels to define the proximal limits of the lymphatic clearance, followed by rectal mobilisation with sharp dissection under direct vision in the avascular plane outside the mesorectum excising the entire mesorectum and leaving the autonomic nerve plexuses intact. This surgical innovation has been shown to reduce local recurrence dramatically, while maximising the chances of sphincter-preserving surgery.
Permanent impotence in men has been reported to be almost universal in some series of abdominoperineal excisions of rectum and occurs in up to half of all men after anterior resection of the rectum for rectal cancer. The incidence of permanent bladder denervation after rectal excisional surgery has been reported to be up to 19% in some series. The presumed mechanism for sexual and urinary dysfunction is damage to the pelvic autonomic parasympathetic and/or sympathetic nerves during surgery.
The risk of sympathetic nerve damage occurs in the abdomen during ligation of the inferior mesenteric artery pedicle, and high in the pelvis during initial posterior rectal dissection adjacent to the large hypogastric nerves. Lower down, risk to the parasympathetic nerves occurs while dissecting laterally near the pelvic plexus, and during deep dissection of the anterior aspect of the rectum away from the seminal vesicles and prostate near the cavernous nerves. The anterior dissection is thought to be the point of highest risk to the nerves governing erectile function.
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