Faecal incontinence is the inability to control your bowel movements, causing stool to leak unexpectedly from your rectum. Faecal incontinence can range from occasional leakage of a small quantity of stool to a complete loss of bowel control. An incompetent anal sphincter can be a primary factor in bowel incontinence.
Faecal incontinence can have several causes, including:
Constipation is one of the most common causes of faecal incontinence. Constipation causes large, hard stools to become lodged in the rectum. Watery stool can then leak out around the hardened stool. Constipation also causes the muscles of the rectum to stretch, which weakens the muscles so they can’t hold stool in the rectum long enough for a person to reach a bathroom.
Faecal incontinence can be caused by injury to one or both of the ring-like muscles at the end of the rectum called the anal internal and external sphincters. The sphincters keep stool inside. When damaged, the muscles aren’t strong enough to do their job and stool can leak out. In women, the damage often happens when giving birth. The risk of injury is greatest if the doctor uses forceps to help deliver the baby or performs an episiotomy, which is a cut in the vaginal area to prevent it from tearing during birth. Hemorrhoid surgery can also damage the sphincters.
Faecal incontinence can be caused by damage to the nerves that control the anal sphincters or the nerves that sense stool in the rectum. If the nerves that control the sphincters are injured, the muscles don’t work properly and incontinence can occur. If the sensory nerves are damaged, they don’t sense that stool is in the rectum so you won’t feel the need to use the bathroom until stool has leaked out. Nerve damage can be caused by childbirth, a long-term habit of straining to pass stool, stroke, physical disability due to injury, and diseases that affect the nerves such as diabetes and multiple sclerosis.
Normally, the rectum stretches to hold stool until you can get to a bathroom. But rectal surgery, radiation treatment, and inflammatory bowel disease can cause scarring that makes the walls of the rectum stiff and less elastic. The rectum then can’t stretch as much to hold stool and faecal incontinence results. Inflammatory bowel disease also can irritate rectal walls, making them unable to contain stool.
Diarrhoea, or loose stool, is more difficult to control than solid stool because with diarrhoea the rectum fills with stool at a faster rate. Even people who don’t have faecal incontinence can leak stool when they have diarrhoea.
Abnormalities of the pelvic floor muscles and nerves can cause faecal incontinence.