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Irritable Bowel Syndrome (IBS) Health Center

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Irritable Bowel Syndrome

What Causes IBS?

Two hundred years after the condition was first described, experts still don't completely understand what causes IBS symptoms.

Many experts think that it is a problem of bowel motility -- the muscles in the bowels don't contract normally -- affecting the movement of stool. But some studies don't show that the poor bowel motility correlates with symptoms. Also, drugs that alter motility don't seem to benefit most people with IBS.

Newer studies suggest that in IBS, the colon is hypersensitive, overreacting to mild stimulation by going into spasms. Instead of slow, rhythmic muscle contractions, the bowel muscles spasm. That can either cause diarrhea or constipation.

Another theory suggests that a number of substances that regulate the transmission of nerve signals between the brain and GI tract may be involved. These include serotonin, gastrin, motilin, and others.

Some have also suggested that there is a hormonal component to the condition, as it occurs in women much more frequently than in men. So far, studies have not borne this out.

A number of factors can "trigger" IBS, including certain foods, medicines, the presence of gas or stool, and emotional stress.

How Is IBS Diagnosed?

The diagnosis of IBS relies on the recognition of the symptoms as well as an extensive evaluation to rule out other causes. There are no specific lab tests that can be done to diagnose IBS. Therefore, your health care provider may run some tests to rule out other conditions such as:

  • Food allergies or intolerances, such as lactose intolerance and poor dietary habits.
  • Medications such as high blood pressure drugs, iron, and certain antacids.
  • Infection.
  • Enzyme deficiencies where the pancreas isn't secreting enough enzymes to properly digest or break down food.
  • Inflammatory bowel diseases like ulcerative colitis or Crohn's disease.

The clinical diagnosis of IBS can be made by your doctor after a thorough history and exam and once other metabolic or structural conditions have been eliminated as a cause. Your health care provider may perform one or more of the following tests for further evaluation:

  • Flexible sigmoidoscopy or colonoscopy to look for signs of intestinal obstruction or inflammation.
  • Upper endoscopy if heartburn or indigestion is present.
  • X-rays.
  • Blood testing to look for anemia (deficiency in red blood cells), thyroid problems, and signs of infection.
  • Stool testing for blood or infections.
  • Testing for lactose intolerance or gluten allergy (celiac disease).
  • Specific testing to look for bowel motility problems.

How Is IBS Treated?

Treatment of IBS involves a collaborative effort between the doctor and the patient to manage symptoms and may consist of lifestyle changes and drug treatments.

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