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Irritable Bowel Syndrome - IBS - Symptoms - Treatments

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Updated July 17, 2009

What is irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) is a term used to describe discomfort in the bowel (the colon, or large intestine). Symptoms of IBS may include crampy pain, bloating, gas, mucus in the stool, and changes in bowel habits. Some people with IBS have constipation—infrequent stools that may be hard, dry and painful. Others have diarrhea—frequent loose stools. Some people having alternating constipation and diarrhea. Sometimes a person with IBS has a crampy urge to move the bowels but cannot do so.

You may have heard IBS referred to as "spastic colon" or "spastic bowel." Sometimes IBS is confused with inflammatory bowel diseases such as ulcerative colitis. But IBS is not a disease and does not cause inflammation, bleeding, damage to the bowel, or cancer or other serious diseases. It is called a functional disorder, which means that there is no sign of disease when the colon is examined, but the bowel doesn't work as it should. The cause of IBS is not known, and as yet there is no cure.

Often IBS is just a mild annoyance, but for some people it can be disabling. They may be unable to go to social events, to go out to a job, or to travel even short distances. Most people with IBS, however, are able to control their symptoms through diet, stress management, and medicines.

Who gets IBS?

IBS is a common problem, affecting up to one in five people. However, estimates of the number of people with IBS vary. The majority of people with IBS (perhaps 75 percent) are women. IBS often begins in the teen years or young adulthood but can affect people of any age.

What are the symptoms of IBS?

Symptoms of IBS may include:

  • Crampy pain in the abdomen

  • Constipation

  • Diarrhea

  • Alternating constipation and diarrhea

  • Feeling that you haven't finished a bowel movement

  • Gas

  • Bloating

  • Mucus in the stool

What causes IBS symptoms?

The colon or large intestine is a muscular tube about 6 feet long. It connects the small intestine with the rectum and anus.

The colon absorbs water and salts from digested food after it has traveled from the stomach through the small intestine. The muscles of the colon contract (tighten or squeeze) and gradually move the material toward the rectum. Strong contractions then lead to a bowel movement. Colon contractions are controlled by nerves, hormones, and by electrical activity in the muscles.

Researchers have found that, for unknown reasons, the colons of people with IBS are more sensitive than usual, and react to things that would not bother other people. For example, the muscles may contract too much after eating. These contractions can cause cramping and diarrhea during or shortly after a meal. The nerves can be overly sensitive to the stretching of the bowel (because of gas, for example), causing cramping or pain. Diet and stress play a role in IBS for many people, causing symptoms or making them worse.

In women, IBS symptoms may be worse during their menstrual periods, so hormone changes may be involved. Sometimes IBS symptoms appear after another illness.

How is IBS diagnosed?

IBS usually is diagnosed after bowel disease has been ruled out. Your doctor will probably take a complete medical history, do a physical exam, and check for blood in your stool. Other diagnostic tests such as blood tests, x-rays or a colonoscopy (viewing the colon through a flexible tube inserted through the anus) may be done if needed.
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