Normally the need to use the toilet is controlled using sphincter muscles and nerves in and around the rectum and anal canal. When there is need to pass a stool, the nerves send a message to the sphincter muscles telling them to relax and open the anus.

If the timing for this isn't convenient, perhaps because a toilet isn't close by, the brain sends a message to stop the muscles relaxing. You usually aren't aware of doing this until the rectum becomes very full and a specific conscious effort is needed to keep the anus closed.

Faecal incontinence is where the muscles and nerves do not work properly. This can be caused by a number of factors:

Diet - Anything that makes the faeces more liquid than normal (e.g. alcohol) can make it harder to hold in. Foods that increase flatulence can also sometimes cause leakage, as the anus has to relax to let out gas.

Irritable bowel syndrome (IBS) - With IBS the bowel muscle is very sensitive and squeezes very strongly, often not at a convenient time which can be hard to control. The need to rush to the toilet when you have the urge to pass stools, or even when you pass wind, can sometimes cause leakage if this isn't reached in time.

Childbirth - Post-childbirth, one in ten women has problems controlling when they pass wind or stools. As with urinary incontinence, it's more common in older mothers, and women who have larger babies. The problem is mainly caused by damage to the anal muscles during birth, or because of the episiotomy cut that is made to help deliver the baby.

Age - The sphincter muscles get weaker with age, which makes it harder to control the need to go to the toilet. Older people with mental health conditions such as dementia may also have trouble recognising when they need to pass stools.

Constipation - Constipation happens when hardened faeces build up in the lower bowel, watery faeces can then leak around them which are difficult to control. Constipation is often the real cause of faecal incontinence especially the elderly.

Medication - Certain medications, for example those containing magnesium trisilicate, make the faeces looser or cause diarrhoea. Over-use of laxatives can also have the identical effects. A GP should be consulted if you are having problems with faecal incontinence and are taking any medication as they can check if this might be a side-effect and if necessary suggest an alternative.

Diarrhoea - Loose stools are more difficult to control than solid stools which can lead to leakage.

Damage to neurological system - Conditions such as a stroke, epilepsy, multiple sclerosis or other conditions which affect the connections between the brain, the nervous system and the sphincter muscles prevent the messages being received correctly and lead to lack of control of the sphinter muscles.

Lower bowel disorders - Conditions such as haemorrhoids, cancer and anal fistula/ fissure can also lead to faecal incontinence.