Fecal incontinence is rarely due to a single factor.

The International Foundation for Functional Gastrointestinal Disorders (IFFGD) has a good  web page that explains about fecal incontinence:

http://www.aboutincontinence.org/site/about-incontinence/causes-of-incontinence/

Fecal incontinence is particularly common in women with IBD, who have undergone surgery for IBD. As mentioned above, the causes of fecal incontinence can be multfactorial, and in women, may include one or a combination of the following: diarrhea that overcomes the anal sphincters, incompetence of the anal sphincters due to destruction from the inflammatory process of the bowel disease, damage from previous surgery, or injury during a delivery, or, recto-vaginal fistulas.

Hope