Abstracts
1998 Digestive Disease Week

#1009

A PUDENDAL NERVE INNERVATED SARTORIUS NEOANAL SPHINCTER. A CANINE MODEL. Denis CNK Nyam, Department of Colorectal Surgery, Singapore General Hospital.

Hypothesis: The pudendal nerve can act as a natural stimulator for neoanal sphincter reconstruction and restoration of fecal continence following abdominal perineal resection.

Aim: To investigate the clinical and physiological effect of pudendal nerve-nerve to skeletal muscle anastomosis in a canine neoanal sphincter model.

Material & Method: 10 canines underwent a perineal protectomy and a perineal colostomy. A neoanal sphincter was constructed by wrapping a pedicled sartorius muscle transposed from the right leg of each dog. The electromyography characteristics and nerve potentials were recorded and muscle biopsied for histology prior to transposition. Similar tests were performed when the dogs regained continence or at 4 months. In 6 dogs, the nerve to the sartorius muscle was transected and anastomosed to the pudendal nerve. The remaining 4 dogs had a muscle transposition without nerve anastomosis (control group).

Result: Cannines with the nerve transposition were more continent and able to defacate in one corner of the cage. Semi qualitative scoring confirmed a higher continence score in the nerve transposition group. Similar differences were observed in the histological structure. Conversion of muscle type from predominantly fast twitch Type I to slow twitch Type II fibers was observed. This was paralleled by a change in electromyography and twitch pattern of the muscle to reassemble that of the original anal sphincter.

Conclusion: The pudendal nerve can be used to innervate a transposed skeletal muscle neosphincter. This results in a change of muscle type to predominantly Type II slow twitch fibers which are then capable of tetanic contraction without fatigue, necessary for continence.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.