A recent study  investigated the frequency of bladder and sexual dysfunction, secondary to pelvic nerve injury, following laparoscopically assisted and conventional open mesorectal resection for cancer in a randomised trial of laparoscopic vs. open resection. A retrospective analysis of bladder and sexual function before and after operation was performed by means of postal questionnaires and telephone interviews. Of the responders, 40 patients had undergone laparoscopically assisted resection and 40 had had an open operation. No significant deterioration in bladder function following an operation was observed, although two patients in the laparoscopic group required long-term intermittent self-catheterisation. A significant difference in male, but not female, sexual function was noted, with seven of 15 sexually active men in the laparoscopic group reporting impotence or impaired ejaculation, compared with only one of 22 patients having an open operation. All patients with bladder or sexual dysfunction in the laparoscopic group had resection of either bulky or low rectal cancers. It was therefore suggested that laparoscopically assisted rectal resection is associated with a higher incidence of male sexual dysfunction, but not bladder dysfunction, than the open approach. This has implications, particularly for sexually active males with bulky or low rectal cancers, when deciding the best operative approach.
Other continence-related problems can occur after restorative rectal cancer surgery or any type of low anastomoses due to the use of the circular stapling device. In fact the passage of the stapler through anal sphincter can cause a stretching of anal sphincter and consequent injury. By comparison, the overall results reported in recent series with stapled anastomosis appear to be more favourable than those obtained after handsewn anastomoses. The reason that function would be better with the use of a stapling technique is obscure. However, in the early series the rate of anastomotic dehiscence and pelvic sepsis was higher than in series of later years and it is probable that such complications influence the results adversely. As regards direct trauma to the sphincter complex, anal dilatation performed during these surgical procedures is a frequent cause of incontinence, particularly in patients submitted to a forceful finger dilatation . A forceful dilatation of the external sphincter and puborectalis muscle results in profound and persistent fall in anal canal pressure  and it has been associated with severe damage to the IAS on anal ultrasonography . Another factor might be that the criteria of selection probably vary in different samples as indicated by a varying mean age of the patients. In our experience the functional results after LAR are far from satisfactory when analysed in an unselected samples. During the first month the majority of the patients suffered from increased frequency, pronounced urgency and a good deal of incontinence for faeces and flatus. Although the function gradually improved during the course of one year, about 50% of our patients had permanent disturbances of continence.
Finally, low colorectal or colo-anal anastomoses determine a new anatomical shape of the pelvic region characterised by an increase of the anorectal angle. This condition, in association with the other mentioned factors, is able to cause more or less marked post-operative incontinence. A further factor that could interfere with continence control is the integrity of the anal canal mucosa with loss of the discriminatory sensitivity between flatus and stools. Pathophysiologic studies into colo-anal and ileoanal anastomoses with or without mucosectomy  would demonstrate that the absence of the mucosa does not influence the anal canal sensitivity threshold significantly, provided that the sphincter anatomic and functional integrity and reservoir function are preserved.
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