Paper Presentations: AUGS Abstracts: 2005 26th Annual Scientific Meeting of The American Urogynecologic Society
To determine the relative contributions of prolonged vaginal distension and anal sphincter transection on contractile properties of the external anal sphincter (EAS).
Young female virginal rats were randomized into 4 treatment groups (sham, vaginal distension, transection of anal sphincter plus repair, or combined distension/transection repair). After 3 weeks, the anal sphincter complex was analyzed for peak force of twitch contraction, peak tetanic force, fatigue and maximal responses to electrical field stimulation (EFS). Each sphincter was serially cross-sectioned at 100 um intervals and stained with H & E to evaluate sphincter integrity. Statistical analysis was performed by using ANOVA (Student-Neuman-Keuls) and Chi-square.
Neurophysiologic function of EAS from animals with vaginal balloon distension was similar to sham. Maximal tetanic and EFS force generation was decreased in the EAS after transection/repair predominantly due to compromise of EAS function in 6 of 12 animals. Although serial sections indicated disruption or attenuation of EAS muscle fibers in compromised sphincters, similar histologic findings were also observed in some tissues with excellent sphincter function. In contrast, tetanic forces and maximal EFS contractions were decreased significantly in EAS from animals with combined injury. Sphincter function was severely compromised in 9 of 9 animals with combined injury. Fatigability of the sphincter was more pronounced in the combined injury group.
CONCLUSION: Data from this investigation indicate that combination vaginal distension/laceration (with repair) results in severe compromise of EAS function. EAS function was compromised in all animals that underwent combined injury and in 50% of animals that underwent episiotomy repair alone. These data suggest that injury imposed by prolonged vaginal distension further compromises function of a lacerated/repaired anal sphincter.