Preservation of continence after posterior sagittal surgery

An animal study was performed to evaluate the effect of posterior sagittal pararectal mobilization on anorectal sphincter function.

We initially divided 11 juvenile pigs into 3 groups: group 1-anesthesia alone (3), group 2-posterior sagittal incision alone (4) and group 3-posterior sagittal incision with unilateral pararectal dissection (4). Two animals in group 1 subsequently underwent posterior sagittal incision with circumferential pararectal dissection (group 4). The anal canal was preserved intact in all animals. Anorectal sphincter manometry was performed preoperatively, and 2, 4, 8 and 12 weeks postoperatively. Electromyography was performed 12 weeks postoperatively. Anorectal sphincter muscle complexes were harvested for histological examination.

All animals had postoperative bowel continence. Postoperatively manometry revealed no difference from preoperative measurements in all study groups (p = 0.90). Electromyography and histological examination of the anorectal sphincters were normal in all but 2 animals. Denervation injury and histological atrophy were detected after repair of inadvertent enterotomy in 1 animal following unilateral pararectal dissection, and polyphasic motor unit potentials implying reinnervation were detected in another after circumferential pararectal mobilization.

These results indicate that posterior sagittal incision and unilateral pararectal mobilization cause no permanent injury to the anorectal sphincter. However circumferential pararectal dissection or repair of a rectal injury may cause measurable changes in sphincter function.