Bowel incontinence, also called fecal incontinence, can be caused by injury to the anal sphincter, which is the muscle located at the end of the rectum, according to Mayo Clinic. Other causes of bowel incontinence include nerve damage, diarrhea, constipation and loss of the rectum's storage capacity. Surgery can be an additional cause.
When the rings of muscle located at the rectum's end sustain injury, this damage makes it hard to hold stool in, as noted by Mayo Clinic. This damage may result from childbirth, especially if the baby is delivered using forceps or if the mother has an episiotomy to assist with delivery.
Childbirth and diseases such as multiple sclerosis and diabetes can cause nerve damage in the rectal area, leading to incontinence of the bowels, as reported by Mayo Clinic. Nerve damage may also result from stroke or spinal cord injuries. Chronic constipation can lead to impacted stool that weakens and stretches the rectal muscles, causing nerve damage and eventual incontinence.
Scarring of the rectal walls from inflammatory bowel disease, surgery or radiation therapy can lead to loss of rectal storage capacity, as stated by Mayo Clinic. In turn, this allows fecal matter to leak out. The same is true of other surgeries to the anal or rectal region that damage nerves.