Bowel Conditions



Constipation without bowel leakage is a subject in its own right and there is not space to deal with it here. Mild constipation will often respond to changes in diet, such as adding more fibre and fluids, or to gentle medication such as Fybogel, Movicol or Regulan and to an increase in exercise. Severe constipation needs professional advice. You can read more about constipation here.

Irritable Bowel Syndrome (IBS)

IBS is a common bowel problem, affecting up to one in five of the population. Most commonly it causes abdominal discomfort, with an alteration in bowel habit (diarrhoea or constipation, or alternating between constipation,scars and diarrhoea). People with diarrhoea associated with Irritable bowel syndrome may have difficulty in getting to the toilet in time, or difficulty controlling wind. There is not one simple treatment for IBS, but some medications, diets or complimentary therapies are helpful for some people. Further information is available in the UK from the IBS Network and in the USA from the International Foundation for Functional Gastrointestinal Disorders.

-Childbirth Injuries

Sometimes damage to the muscles of the anal sphincter is accidentally caused during childbirth, especially if forceps were needed to help the baby to be born. Sometimes exercises will help regain the function of damaged muscles. If the damage to the muscles is extensive, an operation may be needed to repair them.


Crohn’s Disease

See inflammatory bowel disease below.

Ileo-Anal Pouch Operation

An ileo-anal pouch operation may be done for people who need the large bowel removed because of disease. A few people have trouble with leakage from the anus after this operation.

Inflammatory Bowel Disease (IBD)

IBD includes ulcerative colitis, Crohn’s disease and other less common diseases involving inflammation of the lining of the bowel wall. Diarrhoea is often associated with IBD, especially in the acute phase. This can cause tremendous urgency and accidents from the bowel if the toilet is not reached in time. Further information is available from the National Association for Colitis & Crohn’s Disease.

Spinal Cord Injury

Bowel control is a major concern for many people after a spinal cord injury. There are often problems both with emptying the bowel and with control. Detailed advice is available on a site we have developed for the Spinal Injuries Association.


Normal Bowel Function


Most adults take bowel control for granted and need to give it little thought except for the few minutes a day that are spent emptying the bowel on the toilet. However, bowel control is actually a complex and incompletely understood process, involving delicate co-ordination of many different nerves and muscles.

The bowel is part of the digestive system and its’ role is to digest the food that we eat, absorb the goodness and nutrients from the digested food into the blood stream and then to process and expel the waste products from the food that the body cannot use. This process starts at the mouth and finishes at the anus or back passage (FIGURE 1).

FIGURE 1 The bowel

The small bowel, or small intestines is the part of the bowel where the useful parts of food are absorbed. The small bowel delivers 1-2 pints (500-1,000mls) of waste to the colon per day. The colon, or large bowel is the waste processing part of the system. This waste is the consistency of thick pea soup when it enters the beginning of the colon. It is the job of the colon to absorb fluid from this waste and, as it moves around the colon, to gradually form it into stools (also called feces or bowel motions). Stool consistency can vary between hard lumps to very loose or mushy, often depending how long the stools have been in the colon and how much water has been absorbed from them. Ideally stools should be formed into soft smooth sausage-shapes which are comfortable to pass. See chart for more information .

The left side of the colon and the rectum are the “storage tank” at the end of the large bowel. Normally the rectum is relatively empty. Stool does not enter the rectum from the colon on a continuous basis, but as a result of mass movements, which happen from time to time, especially before the need to go to the toilet is experienced. These mass movements are major waves of pressure, which can move stool through the whole length of the colon, like toothpaste being squeezed along a tube (FIGURE 2). Often a large part of the contents of the colon arrives in the rectum at once.

These mass movements are often triggered by the so-called gastro-colic response. Food arriving in the stomach when you eat a meal sets off a pressure wave in the colon some minutes later. This can lead to the need to empty the bowel, sometimes urgently, soon after eating. For many people the bowel is relatively quiet at night. The first meal of the day, together with the physical activity involved in getting out of bed and washing and dressing, stimulates contractions in the colon and mass movements. This leads to a “call to stool”, the feeling that the bowel needs emptying, shortly after breakfast.

Food usually takes an average of 1-3 days to be processed and up to 90% of that time is spent in the colon.

FIGURE 2 Mass movements in the colon

How often should I empty the bowel?

There is no right or wrong answer to this. There is a very wide range of “normal” bowel function between different people. It is by no means essential to have one bowel action per day, and indeed it is probably a minority of the total population who has this. Some people always go several times per day; others have several days between bowel actions. As long as stools are passed without excessive urgency (needing to rush to the toilet), with minimal effort and no straining, and without the use of laxatives, bowel function may be regarded as normal.

Perception of what is normal is based on personal experiences and growing up with other people. Most of us do not discuss bowel habit with our friends, or even our family. A few people become obsessed with the need for a daily bowel action and spend excessive amounts of time in the toilet or take laxatives to achieve this. Often this is unnecessary.

How is bowel emptying controlled?

FIGURE 3 Internal & External Sphincter Muscles

There are two rings of muscle around the anus or exit from the bowel (FIGURE 3). These two rings of muscle form the anal sphincter and are designed to hold in the bowel contents at all times except when you are sitting on the toilet and trying to empty the bowel.

The internal anal sphincter is an internal muscle responsible for keeping the anal canal closed at all times except when there is an urge to empty the bowel. You do not have to think about keeping this muscle closed, it happens automatically.

The external anal sphincter is the muscle that you use to hold on when the rectum is full and you feel that you need to empty the bowel.

When stool enters the rectum the internal anal sphincter muscle automatically relaxes and opens up the top of the anal canal. This is normal and allows stool to enter the upper anal canal to be “sampled” by the very sensitive nerve cells in the upper anal canal (FIGURE 4). People with normal sensation can easily tell the difference between wind (gas, also called flatus), which can safely be passed if it is socially convenient without fear of soiling, diarrhea (very loose or runny stools needing urgent attention and access to a toilet) and a normal stool. Most people just know what is in the rectum without really having to think about it.

Around the internal anal sphincter is the external anal sphincter, which is much thicker. This is the muscle around the anus that you can deliberately squeeze. Just like the muscles in the arm or leg, a person can decide when to use this muscle.

FIGURE 4 Internal sphincter relaxation when the rectum is full

FIGURE 5 External sphincter squeezes
If a normal stool is sensed and it is not convenient to find a toilet at that moment, bowel emptying is delayed by squeezing the external anal sphincter. Squeezing the external sphincter ensures that the stool is not simply expelled as soon as it enters the rectum, and in fact the stool is pushed back up out of the anal canal (FIGURE 5). For most people this is not a deliberate action – you should not need to think, “I must squeeze my anal sphincter muscles so that I do not have a bowel accident” – but this is actually what you do, subconsciously without really thinking about it.

This external sphincter squeeze does not need to last all the time until the toilet is found. Stool is propelled back into the rectum, and the rectum relaxes and so the urge to empty the bowel is resisted and wears off.

For most people, an urge to empty the bowel is felt, but if the time and place are not right, it is possible to delay bowel emptying, and the feeling of needing to go wears off very soon. Most people can then forget about the bowel for a while, and some can put off bowel emptying almost indefinitely, but may get reminders that the bowel is full at intervals until it is emptied. Continually resisting the urge to empty the bowel or ignoring the call to stool can lead to constipation, as the longer the stools stay in the colon and rectum, the more fluid is absorbed and the harder the stools become.

For this mechanism to work properly you need several things:

  • the nerves of the rectum and anus need to be sending the right messages to your brain so that you can feel when stool or gas arrives in the rectum and can send messages to the muscles that you want to hold on;
  • the internal and external anal sphincters need to be undamaged and working properly;
  • the stools should not be too soft or loose so that the sphincters can cope with holding on, but not so hard so that they are difficult to pass;
  • and you need the physical ability to get to and onto a toilet and to hold on until the correct place is reached.

As you can imagine, this is a delicate system and unfortunately there are many things that can go wrong with it.