Vaginal Distention Rodent Model for Fecal Incontinence: A Pilot Study on the Effect on Defecation Behavior

Objectives Vaginal balloon inflation simulates the compressive forces on the pelvic floor during the second phase of natural delivery. The foremost use of this animal model of vaginal distention (VD) is to study the mechanisms underlying urinary incontinence. As damage to the pelvic floor during natural birth is a common cause of fecal incontinence, the present paper aimed to investigate the effect of VD on defecation behavior in adult rats. Methods Vaginal distention was performed in 8 rats for 2 hours, and in 3 rats for 4 hours, and sham inflation was performed in 4 rats. With the use of a latrine box in the rat home-cage and 24/7 video tracking, the defecation behavior was examined. The time spent in and outside the latrine was monitored for two weeks preoperatively and three weeks postoperatively, and a defecation behavior index (DBI; range: 0 [continent] to 1 [incontinent]) was defined. Pelvic floor tissue was collected postmortem and stained with hematoxylin and eosin. Results Vaginal balloon inflation for 2 hours resulted in fecal incontinence in 29% of the animals (responders) whereas the DBI scores of non-responders (71%) and control animals did not change in the postoperative phase compared with the baseline score. A 4-hour balloon inflation resulted in fecal incontinence in 1 animal and caused a humane endpoint in 2 animals with markedly more tissue damage in the 4-hour responder compared with the 2-hour responders. Conclusions Vaginal balloon inflation, with an optimum duration between 2 and 4 hours, can be used as a model to study changes in defecation behavior in rats induced by pelvic floor damage.