Causes of bowel incontinence 

Bowel incontinence is usually caused by a physical problem with the parts of the body that control the passage of stools.

The most common problems are:

  • Problems with the rectum: the rectum (where stools are held) is unable to store stools properly until it is time to go to the toilet.
  • Problems with the sphincter muscles: the muscles at the bottom of the rectum do not work properly.
  • Nerve damage: the nerve signals sent from the rectum do not reach the brain.

These problems are explained in more detail below.

Problems with the rectum


Constipation is a leading cause of bowel incontinence.

In cases of severe constipation, a large, solid stool can become stuck in the rectum. This is known as faecal impaction. The stool then begins to stretch the muscles of the rectum, weakening them.

Watery stools can then leak around the stool and out of the bottom, causing bowel incontinence. This is called overflow incontinence and occurs most commonly in people who are elderly and frail.


It is more difficult for the rectum to hold liquid stools (diarrhoea) than solid stools, so people with diarrhoea (particularly recurring diarrhoea) can develop bowel incontinence.

Conditions that can cause recurring diarrhoea include:

These conditions can also cause scarring of the rectum, which can lead to bowel incontinence.

Medications such as lansoprazole and metformin can also cause loose stool.

Problems with the sphincter muscles

The sphincter muscles at the bottom of the rectum control the passage of stools. Bowel incontinence can occur if these muscles become weakened or damaged.

Childbirth is one of the most common causes of damage to the sphincter muscles and a leading cause of bowel incontinence. During a vaginal delivery of a baby, the sphincter muscles can become stretched and damaged, particularly as a result of a forceps delivery.

Sphincter muscles can also become damaged through injury, or damage that arises as a complication of bowel or rectal surgery.

Nerve damage

Bowel incontinence can also be caused by a problem with the nerves connecting the brain and the rectum. A nerve problem can mean your body is unaware of stools in your rectum, and may make it difficult for you to control your sphincter muscles.

Damage to these nerves is related to a number conditions, including:

An injury to these nerves, such as a spinal injury, can also lead to bowel incontinence.

Other health conditions

Bowel incontinence does not always result from physical damage to a part of the bowel or the nerves. In some cases, it may result from a health condition such as dementia or a severe learning disability that causes the person to lose the ability to control their bowel properly.

A physical disability can also make it difficult to get to the toilet before passing a stool.

Are bowel problems a sign of something more serious?

There is a small chance your bowel problems are a sign of bowel cancer or another serious condition, so make sure you discuss them with your GP.

Page last reviewed: 13/03/2013

Next review due: 13/03/2015