rough for imperforate anus and has one to three bowel movements per day with no soiling in between has a great potential for future fecal continence. The child shows signs that he is "feeling" while having a bowel movement as he pushes. On the other end of the spectrum, a child who suffers from fecal incontinence passes stool constantly without any evidence of pushing or feeling. A child with a normal bowel movement pattern is trainable, whereas a child with the second pattern will likely need a bowel management program. For that child, one should not expect him to achieve voluntary bowel control.
When evaluating the results of the treatment of anorectal defects, we feel that one cannot group patients according to the traditional nomenclature into "high," "intermediate," and "low" defects, as malformations classified in a same group can have different treatments and different prognoses. For instance, rectoprostatic fistula and bladderneck fistula, both considered as "high" defects are actually very different. We believe that an anatomic classification would have more clinical value. The functional results of the repair of anorectal anomalies seem to have significantly improved since the advent of the posterior sagittal approach. However, the results of this approach are difficult to compare with those of other methods because terminology and classification are not consistent [32, 33].
Fecal continence depends on three main factors: Voluntary sphincter muscles, anal canal sensation, and colonic motility.
Voluntary muscle structures
In the normal patient, the voluntary muscle structures are represented by the levators, muscle complex, and external sphincter. Normally, they are used only for brief periods, when the rectal fecal mass reaches the anorectal area, pushed by the involuntary peristaltic contraction of the rectosigmoid motility. This voluntary contraction occurs only in the minutes prior to defecation, and these muscles are used only occasionally during the rest of the day and night.
Patients with anorectal malformations have abnormal voluntary striated muscles with different degrees of hypodevelopment. Voluntary muscles can be used only when the patient has the sensation that it is necessary to use them. To appreciate that sensation, the patient needs information that can only be derived from an intact anal sensory mechanism, a mechanism that many patients with anorectal malformations lack.
Exquisite sensation in normal individuals resides in the anal canal. Except for patients with rectal atresia, most patients with anorectal malformations are born without an anal canal; therefore, sensation does not exist or is rudimentary.
It seems that patients can perceive distention of the rectum but this requires a rectum that has been properly located within the muscle structures. This sensation seems to be a consequence of stretching of the voluntary muscle (proprioception). The most important clinical implication of this is that liquid stool or soft fecal material may not be felt by the patient as it does not distend the rectum. Thus, to achieve some degree of sensation and bowel control, the patient must have the capacity to form solid stool.
Perhaps the most important factor in fecal continence is bowel motility; however, the impact of motility has been largely underestimated. In a normal individual, the rectosigmoid remains quiet for variable periods of time (one to several days), depending on specific defecation habits. During that time, sensation and voluntary muscle structures are almost not necessary because the stool, if it is solid, remains inside the colon. The patient feels the peristaltic contraction of the rectosigmoid that occurs prior to defecation. Voluntarily, the normal individual can relax the striated muscles which allow the rectal contents to migrate down into the highly sensitive area of the anal canal. There, accurate information is provided by the anal canal concerning the consistency and quality of the stool. The voluntary muscles are used to push the rectal contents back up into the rectosigmoi