Information about IBS

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Irritable bowel syndrome (IBS) is one of the most common—and frequently misunderstood—digestive disorders. One in five adults in the United States has symptoms of IBS, yet only a small number of people with symptoms seek treatment.

The good news is that:

  1. IBS can often be effectively managed once an accurate diagnosis is made—although you will require a number of tests to rule out other diseases; and
  2. it appears that the disorder does not cause long-term damage to the digestive tract or lead to serious complications.

Causes of irritable bowel syndrome

The cause of IBS is not well understood. Some researchers have proposed that IBS may result from malfunctions in the rhythmic muscle contractions that propel food through the small and large intestines. Contractions that are too strong can push food contents through the intestines too quickly, causing diarrhea and bloating; weak contractions can lead to constipation.

Because women are diagnosed with IBS about three times more often than men, some experts hypothesize that symptoms may be related to hormone levels. Other proposed causes include hypersensitivity to pressure in the small and large intestines, an imbalance in neurotransmitters (chemicals found in both the brain and digestive tract), and infection.

Psychological factors may also play a role. IBS and mental stress appear to be closely related, and people with depression or anxiety tend to be more susceptible to IBS. Studies also show an increased risk of IBS in women who have been physically or sexually abused.

Symptoms of irritable bowel syndrome

The symptoms of IBS usually first appear during the teenage years or young adulthood, although the condition can develop at any time, even in older adults. One of the most common symptoms is abdominal discomfort or pain, accompanied by diarrhea, constipation, or alternating bouts of constipation and diarrhea.

Other symptoms include abdominal bloating, a feeling of incomplete emptying of the bowels after passing stool, and mucus in the stool. If you have IBS, you may find the symptoms distressing and disruptive to your life. The severity of symptoms varies: Most people experience mild symptoms, although they can become more severe and even disabling at times.

Some women report that IBS symptoms are worse before and during their menstrual periods. The symptoms may even awaken some people in the middle of the night.

Diagnosis of irritable bowel syndrome

IBS is difficult to diagnose because the disease causes no known physical abnormalities that doctors can identify through physical exams, imaging studies, or lab testing. As a result, doctors make a diagnosis only after ruling out other conditions.

If you have symptoms suggestive of IBS, your doctor will take a medical history, perform a physical exam, and order blood tests. A barium enema, sigmoidoscopy, or colonoscopy may be needed to view the rectum and colon.

Once your doctor determines that your abdominal pain is not due to a physical abnormality, two of the following three criteria must be met to make a diagnosis of IBS:

  • bowel movements alleviate pain
  • pain is accompanied by constipation or diarrhea
  • pain is associated with a change in the form of the stool (watery, loose, or pellet-like)

These symptoms must be present, all of the time or occasionally, for at least three months.

Because the symptoms of IBS overlap with so many other digestive disorders, people with the syndrome are sometimes misdiagnosed. IBS can easily be confused with

  • diverticulitis
  • colon cancer
  • intestinal obstruction
  • ulcerative colitis
  • Crohn's disease
  • gastrointestinal infection
  • celiac disease
  • lactose intolerance

Treatment of irritable bowel syndrome

Treatment of IBS focuses on relieving the most bothersome symptoms.

Publication Review By: H. Franklin Herlong, M.D.

Published: 27 Mar 2011

Last Modified: 22 Sep 2015