Systematic Review of Animal Models Used in Research of Origins and Treatments of Fecal Incontinence

Fecal incontinence is a common disorder, but its pathophysiology is not completely understood.The aim of this review is to present animal models that have a place in the study of fecal incontinence.A literature review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines performed in August 2016 revealed 50 articles of interest. Search terms included fecal/faecal incontinence and animal model or specific species.Articles not describing an animal model, in vitro studies, veterinary literature, reviews, and non-English articles were excluded.The articles described models in rats (n = 31), dogs (n = 8), rabbits (n = 7), and pigs (n = 4).Different fecal incontinence etiologies were modeled, including anal sphincter lesions (33 articles) ranging from a single anal sphincter cut to destruction of 50% of the anal sphincter by sharp dissection, electrocautery, or diathermy. Neuropathic fecal incontinence (12 articles) was achieved by complete or incomplete pudendal, pelvic, or inferior rectal nerve damage. Mixed fecal incontinence (5 articles) was modeled either by the inflation of pelvic balloons or an array of several lesions including nervous and muscular damage. Anal fistulas (2 articles), anal sphincter resection (3 articles), and diabetic neuropathy (2 articles) were studied to a lesser extent.Bias may have arisen from the authors' own work on fecal incontinence and the absence of blinding to the origins of articles.Validated animal models representing the main etiologies of fecal incontinence exist, but no animal model to date represents the whole pathophysiology of fecal incontinence. Therefore, the individual research questions still dictate the choice of model and species.