Bowel incontinence is usually caused by a physical problem with the parts of the body that control the bowel.
The most common problems are:
- problems with the rectum – the rectum is unable to retain poo properly until it's time to go to the toilet
- problems with the sphincter muscles – the muscles at the bottom of the rectum don't work properly
- nerve damage – the nerve signals sent from the rectum don't reach the brain
These problems are explained in more detail below.
It's important to discuss any bowel problems with your GP as there's a small chance they could be a sign of a more serious condition, such as bowel cancer.
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 leak around the stool and out of the bottom, causing bowel incontinence. This is called overflow incontinence and happens most commonly in elderly people.
Repeated straining caused by constipation or faecal impaction can also lead to rectal prolapse, when part of your lower intestine falls out of place and protrudes from your bottom. Rectal prolapse may also lead to bowel incontinence.
It's difficult for the rectum to hold liquid stools (diarrhoea), 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.
Haemorrhoids (piles) are enlarged blood vessels inside or around the bottom (the rectum and anus). Symptoms include discomfort, itching, bleeding or a lump hanging down outside of the anus.
In severe cases, haemorrhoids may lead to bowel incontinence.
Problems with the sphincter muscles
The sphincter muscles at the bottom of the rectum control the bowel. Bowel incontinence happens if these muscles become weakened or damaged.
Childbirth is a common cause of damage to the sphincter muscles and a leading cause of bowel incontinence. During a vaginal birth, the sphincter muscles can become stretched and damaged, particularly as a result of a forceps delivery. Other causes include a large baby, the baby being born with the back of their head facing the mother's back (occipitoposterior position) and a long labour.
Sphincter muscles can also become damaged through injury, or damage from bowel or rectal surgery.
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 of conditions, including:
An injury to these nerves, such as a spinal injury, can also lead to bowel incontinence.
Other health conditions
In some cases, bowel incontinence may result from a health condition such as dementia or a severe learning disability that causes the person to lose bowel control.
A physical disability can also make it difficult to get to the toilet in time.