This decrease in tone allows the rectal contents to reach the sensitive anal mucosa, allowing a distinction between gas, fluid and faeces. Goligher et al.  suggested that at least 6-8 cm of intact anorectum is necessary for maintenance of an intact recto-anal reflex. This assumption has been challenged by Lane and Parks, who showed the response in 9 out of the 12 patients after colo-anal anastomosis, some of them only after more than one year had elapsed, however. The reappearance of the recto-anal inhibitory reflex, which has also been observed in one of our series of patients, might at least partly explain the subjective improvement occurring as late as one to two years after surgery.
Many of the undesirable consequences of anterior resections and straight low rectal or colo-anal anastomoses are believed to be due to loss of the rectum's reservoir capacity , but other significant factors are the effect of radiotherapy, septic complications, trauma to the sphincter complex and the damage of nerve pathways.
The influence of different factors on functional results will be considered in the following paragraphs.
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