What is Irritable bowel syndrome?

Irritable bowel syndrome

What is irritable bowel syndrome?

Irritable bowel syndrome (IBS) stops your bowels from working properly. This can cause pain in your abdomen, cramps, bloating, constipation or diarrhea.

IBS can make you anxious. A lot of people worry that their symptoms are linked to something serious, like cancer. But IBS doesn't lead to more serious illnesses.

There's no cure for IBS, but treatment can help your symptoms. There are also things you can do for yourself that may help.

IBS is also called spastic colon, nervous colon or irritable colon.

Key points for people with irritable bowel syndrome

IBS is very common. It affects about 1 in 6 people, and mostly affects women.
IBS can cause a lot of pain. But it doesn't lead to more serious diseases, such as cancer.
There's no cure for IBS. But there are treatments that can improve your symptoms.
Your doctor may try to help your symptoms without using drugs, and will probably recommend that you take drugs only when you really need them.
If you have IBS, there are things you can do for yourself that might help, such as learning to deal with stress.
Learning as much as you can about IBS will help you cope better.

How your bowels normally work

To understand what goes wrong when you have irritable bowel syndrome, it helps to know a little about how your bowels normally work. Your bowels are also known as your intestines.

Muscles push food through your bowels.

Your bowels form a long tube that runs from your stomach to your rectum. Their job is to break down the food you eat so nutrients can pass into your bloodstream. Once this is done, your bowels carry away the waste.

Your bowels have two parts. These are called the small bowel and the large bowel, or small and large intestine.

The outer wall of your bowels is made up of muscles. Like all muscles, they can contract and relax.

But you can't control how these muscles move. They contract and relax automatically to push food and waste along.

Source:
Martini FH, Ober WC, Garrison CW, et al.
Fundamentals of anatomy and physiology.
5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Here's what happens.

After you eat, food goes down to your stomach and then into your bowels.
Muscles push the food through the small bowel.
The nutrients and water from your food are absorbed into your bloodstream.
The waste that your body doesn't need is left over. It forms solid lumps (stools).
Muscles push the waste through your colon. This is the first 6 feet of your large bowel.
The waste is pushed into your rectum. This is the last 8 to 10 inches of your large bowel.
The food waste leaves your body through your

anus
The anus, which is at the end of the rectum, is where a stool leaves your body when you go to the bathroom. Part of the anus is a muscle that helps you hold in the stool until you are on the toilet.

anus.
Your rectum and anus are surrounded by a ring of muscles called your sphincter muscles. The sphincter muscles relax so you can empty your bowels.

What goes wrong?

Doctors aren't sure what happens in your body when you have irritable bowel syndrome. But they think that the muscles that make up the wall of your bowels don't work in the normal way.

Source:
Gorard DA, Libby GW, Farthing MJ, et al.
Ambulatory small intestinal motility in 'diarrhoea' predominant irritable bowel syndrome.
Gut. 1994; 35: 203-210.

Source:
Kellow JE, Phillips SF.
Altered small bowel motility in irritable bowel syndrome is correlated with symptoms.
Gastroenterology. 1987: 92: 1885-1893.

Source:
Prior A, Maxton DG, Whorwell PJ.
Anorectal manometry in irritable bowel syndrome: differences between diarrhoea and constipation predominant subjects.
Gut. 1990; 31: 458-462.

⁴

Your bowels run from your stomach to your rectum.

Doctors think the movement of these muscles can change in several ways.

The muscles may work faster than normal. This means they push the waste through more quickly. Less water is absorbed from the food, which makes your stools soft and watery. This can cause diarrhea. You may need to go to the bathroom a lot and feel you need to go urgently.
The muscles may push the waste along more slowly. This means that waste can stay in your bowels for a long time. If this happens, too much water is absorbed from the waste. Your stools then become hard and going to the bathroom is uncomfortable.
The muscles may go into spasm. You get spasms when your muscles suddenly contract. The contraction is very strong and can cause painful cramps. If you have spasms, waste or gas from food may get trapped in your bowels. This can make you feel bloated.
The muscles in your bowels may no longer work together with other muscles.

Source:
National Digestive Diseases Information Clearinghouse.
Irritable bowel syndrome.
July 2007. Available at http://digestive.niddk.nih.gov (accessed on 31 July 2008).

⁵ This means the stools don't move smoothly through your bowels. You may get a painful urge to go to the bathroom but find you can't. Or you may go to the bathroom but feel that you haven't completely finished emptying your bowels.

What causes irritable bowel syndrome?

We don't know what causes the muscles of your bowels to stop working properly. There's no obvious cause that doctors can test for, such as an infection. People with irritable bowel syndrome (IBS) don't have any serious abnormality in their bowels. There are probably several different things that act together to cause your symptoms.

Source:
Francis CY, Morris J, Whorwell PJ.
The irritable bowel severity scoring system: a simple method of monitoring irritable bowel syndrome and its progress.
Alimentary Pharmacology and Therapeutics. 1997: 11: 395-402.

⁶

Doctors think that one important cause is a disruption in the messages that are sent between your brain and your bowels. This means that your brain may be sending the wrong messages to the nerves controlling the muscles of your bowels. Your brain may do this when you are under stress or feeling anxious.

Source:
Jones J, Boorman J, Cann P, et al.
British Society of Gastroenterology guidelines for the management of the irritable bowel syndrome.
2000. Available at http://www.bsg.org.uk (accessed on 31 July 2008).

⁷

That doesn't mean IBS is "all in the mind." Your pain and your symptoms are real. But it explains why changes in your mood or emotions could cause the physical symptoms of IBS.

To read more, see Your brain and your bowels.

Some things that seem to cause IBS are:

Sensitive bowels. People with IBS are more sensitive to pain in their bowels.

Source:
Mayer EA, Gebhart GF.
Basic and clinical aspects of visceral hyperalgesia.
Gastroenterology. 1994: 107: 271-293.

⁸

Source:
Mertz H, Naliboff B, Munakata J.
Altered rectal perception is a biological marker of patients with irritable bowel syndrome.
Gastroenterology. 1995; 109: 40-52.

⁹

Source:
Mertz H, Morgan V, Tanner G, et al.
Regional cerebral activation in irritable bowel syndrome and control subjects with painful and non-painful rectal distention.
Gastroenterology. 2000; 118: 842-848.

¹⁰ We don't know exactly why
An infection. An

infection
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.

infection seems to trigger IBS in some people. Almost a quarter of people in one study got IBS after a stomach or bowel infection

Source:
Gwee KA, Leong YL, Graham C, et al.
The role of psychological and biological factors in postinfective gut dysfunction.
Gut. 1999: 44: 400-406.

¹¹
High stress levels. If something stressful happens in your life, it may set off symptoms of IBS. Stressful events could include work difficulties, marriage problems, a death in the family or an operation. Half the people in one study thought their symptoms were triggered by something stressful happening. But not all research shows that stress is a trigger. Some research shows stress can make IBS worse, but not cause it.

Source:
Jones J, Boorman J, Cann P, et al.
British Society of Gastroenterology guidelines for the management of the irritable bowel syndrome.
2000. Available at http://www.bsg.org.uk (accessed on 31 July 2008).

⁷

Why me?

The things that make it more likely you'll get IBS are called risk factors. You're more likely to get IBS if:

You're a woman.

Source:
Chial H, Camilleri M.
Gender differences in irritable bowel syndrome.
Journal of Gender-Specific Medicine. 2002; 5: 37-45.

¹²

Source:
Chang L, Heitkemper M.
Gender differences in irritable bowel syndrome.
Gastroenterology. 2002; 123: 1686-1701.

¹³ Up to twice as many women as men have IBS
Other people in your family have it.

Source:
Locke GR 3rd, Zinsmeister AR, Talley NJ, et al.
Familial association in adults with functional gastrointestinal disorders.
Mayo Clinic Proceedings. 2000; 75: 907-912.

¹⁴

Source:
Levy RL, Jones KR, Whitehead WE, et al.
Irritable bowel syndrome in twins: heredity and social learning both contribute to etiology.
Gastroenterology. 2001; 121: 799-804.

¹⁵

Source:
Morris-Yates A, Talley NJ, Boyce PM, et al.
Evidence of a genetic contribution to functional bowel disorder.
American Journal of Gastroenterology. 1998: 93: 1311-1317.

¹⁶ You're more than twice as likely to get IBS if a close relative has had it.

Source:
Locke GR 3rd, Zinsmeister AR, Talley NJ, et al.
Familial association in adults with functional gastrointestinal disorders.
Mayo Clinic Proceedings. 2000; 75: 907-912.

¹⁴ Studies of twins have found that your

genes
Your genes are the parts of your cells that contain instructions for how your body works. Genes are housed on chromosomes, structures that sit in the nucleus at the middle of each of your cells. You have 23 pairs of chromosomes in your normal cells, each of which has thousands of genes. You get one set of chromosomes, and all of the genes that are on them, from each of your parents.

genes may play a part in whether you get IBS.

Source:
Levy RL, Jones KR, Whitehead WE, et al.
Irritable bowel syndrome in twins: heredity and social learning both contribute to etiology.
Gastroenterology. 2001; 121: 799-804.

¹⁵

Source:
Morris-Yates A, Talley NJ, Boyce PM, et al.
Evidence of a genetic contribution to functional bowel disorder.
American Journal of Gastroenterology. 1998: 93: 1311-1317.

¹⁶ But your upbringing after you are born may be just as important

Source:
Levy RL, Jones KR, Whitehead WE, et al.
Irritable bowel syndrome in twins: heredity and social learning both contribute to etiology.
Gastroenterology. 2001; 121: 799-804.

¹⁵
You have anxiety or depression. Feeling anxious or depressed is more common among people with IBS

Source:
Gwee KA, Leong YL, Graham C, et al.
The role of psychological and biological factors in postinfective gut dysfunction.
Gut. 1999: 44: 400-406.

¹¹
You have been sexually abused. Almost a third of people in one study who consulted a doctor for IBS had been sexually abused.

Source:
Delvaux M, Denis P, Allemand H.
Sexual abuse is more frequently reported by IBS patients than by patients with organic digestive diseases or controls: results of a multicentre inquiry: French Club of Digestive.
European Journal of Gastroenterology and Hepatology. 1997; 9: 345-352.

¹⁷ But this doesn't mean if you have IBS it has been caused by sexual abuse.

Unlike many long-term conditions, IBS is more likely to appear when you are young or middle-aged than when you are older. Symptoms of IBS start before the age of 50 in half of all people who are diagnosed. About 4 in 10 people with IBS are between the ages of 35 and 50.

Source:
Maxwell PR.
Irritable bowel syndrome.
Lancet. 1997; 350: 1691-1695.

¹⁸

Sources for the information on this page:

Martini FH, Ober WC, Garrison CW, et al.Fundamentals of anatomy and physiology.5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Gorard DA, Libby GW, Farthing MJ, et al.Ambulatory small intestinal motility in 'diarrhoea' predominant irritable bowel syndrome.Gut. 1994; 35: 203-210.

Kellow JE, Phillips SF.Altered small bowel motility in irritable bowel syndrome is correlated with symptoms.Gastroenterology. 1987: 92: 1885-1893.

Prior A, Maxton DG, Whorwell PJ.Anorectal manometry in irritable bowel syndrome: differences between diarrhoea and constipation predominant subjects.Gut. 1990; 31: 458-462.

National Digestive Diseases Information Clearinghouse.Irritable bowel syndrome.July 2007. Available at http://digestive.niddk.nih.gov (accessed on 31 July 2008).

Francis CY, Morris J, Whorwell PJ.The irritable bowel severity scoring system: a simple method of monitoring irritable bowel syndrome and its progress.Alimentary Pharmacology and Therapeutics. 1997: 11: 395-402.

Jones J, Boorman J, Cann P, et al.British Society of Gastroenterology guidelines for the management of the irritable bowel syndrome.2000. Available at http://www.bsg.org.uk (accessed on 31 July 2008).

Mayer EA, Gebhart GF.Basic and clinical aspects of visceral hyperalgesia.Gastroenterology. 1994: 107: 271-293.

Mertz H, Naliboff B, Munakata J.Altered rectal perception is a biological marker of patients with irritable bowel syndrome.Gastroenterology. 1995; 109: 40-52.

Mertz H, Morgan V, Tanner G, et al.Regional cerebral activation in irritable bowel syndrome and control subjects with painful and non-painful rectal distention.Gastroenterology. 2000; 118: 842-848.

Gwee KA, Leong YL, Graham C, et al.The role of psychological and biological factors in postinfective gut dysfunction.Gut. 1999: 44: 400-406.

Chial H, Camilleri M.Gender differences in irritable bowel syndrome.Journal of Gender-Specific Medicine. 2002; 5: 37-45.

Chang L, Heitkemper M.Gender differences in irritable bowel syndrome.Gastroenterology. 2002; 123: 1686-1701.

Locke GR 3rd, Zinsmeister AR, Talley NJ, et al.Familial association in adults with functional gastrointestinal disorders.Mayo Clinic Proceedings. 2000; 75: 907-912.

Levy RL, Jones KR, Whitehead WE, et al.Irritable bowel syndrome in twins: heredity and social learning both contribute to etiology.Gastroenterology. 2001; 121: 799-804.

Morris-Yates A, Talley NJ, Boyce PM, et al.Evidence of a genetic contribution to functional bowel disorder.American Journal of Gastroenterology. 1998: 93: 1311-1317.

Delvaux M, Denis P, Allemand H.Sexual abuse is more frequently reported by IBS patients than by patients with organic digestive diseases or controls: results of a multicentre inquiry: French Club of Digestive.European Journal of Gastroenterology and Hepatology. 1997; 9: 345-352.

Maxwell PR.Irritable bowel syndrome.Lancet. 1997; 350: 1691-1695.

This information was last updated on Nov 19, 2008

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