Experimental internal anal sphincter replacement with demucosated colonic plication

Abstract.

Background: Selective re-creation of a new internal anal sphincter could be indicated when the natural one is irreversibly damaged or excised. Methods: In this preliminary experimental work, surgical techniques of internal anal sphincter replacement in pigs were investigated. After preoperative anorectal manometry, surgical procedure was done in two phases: abdominal, mobilization of the colon-rectum to the pelvic floor; and perianal, dissection of the anal canal from the external anal sphincter through the intersphincteric space. The fully mobilized anorectal segment, including the internal anal sphincter, was pulled down through the anus and resected. The distal colonic stump was then demucosated and two types of plications of the demucosated segment were accomplished, each type in three animals. The plicated segment was then returned into the anal canal, inside the external sphincter. Short-term follow-up with clinical and manometric evaluations was performed and, subsequently, histological analysis of the plicated segment, after the animals were sacrificied. Results: None of the animals became incontinent. Anal manometry identified a high-pressure zone and relaxation reflex in the new anal canal. Histologic studies showed hypertrophy of smooth muscle layers without degenerative changes. Conclusion: This study indicates that a plication of colonic smooth muscle wall can re-create a high-pressure zone in the anal canal after the internal anal sphincter has been excised.