The evaluation of functional anorectum for impaired anal sphincters

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In recent years numerous methods for improving anorectal continence in patints with anorectal anomalies have been developed. Severe anorectal incontinence frequently develops in high type anal atresia with sacral anomalies which lead to defective innervation of anal sphincter. The feacal incontinence of these cases is thought to be caused not only by the quantative insufficiency but also by the qualitative dysfunction of the anal sphincter muscles.We established the canine model of feacal incontinence by the sacral nerve denervation. We studied the electrophysiological and histochemical changes in the anal sphincter muscles caused by the sacral nerve denervation.In the electrophysiological examination, we proved that the rectoanal reflex was dependent reaction of the internal sphincter, and that the sacral nerve denervation caused the uninhibited state of innervation in the internal sphincter that the inhibitory neuron and accelance neuron in the sphincter muscles were freed from the central inhibition.In the histochemical examination we proved that the sacral nerve denervation caused abnormalities of both neurofilament and synaptic vesicle expression in the nerve fivers which innervated the internal sphincter muscle.We propose that the electrophysiological and immunohistochemical studies could be available techniques to seek clue the complex pathophisiology of anorectal incontinence in patients with anorectal anomalies, and these studies may give us a hint to develop a new operative procedure for improving continence.