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Irritable Bowel Syndrome (IBS)

Illustration of the anatomy of the digestive system, adult
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What is irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) is an intestinal disorder that causes the following:

  • Crampy pain

  • Gassiness

  • Bloating

  • Changes in bowel habits

IBS has inaccurately been called by many names, including the following:

  • Colitis

  • Mucous colitis

  • Spastic colon

  • Spastic bowel

  • Functional bowel disease

IBS is a functional disorder because there is no sign of disease when the colon is examined. Because doctors have been unable to find an organic cause, IBS often has been thought to be caused by emotional conflict or stress. While stress may worsen IBS symptoms, research suggests that other factors also are important.

IBS often causes a great deal of discomfort and distress, but it is not believed to:

  • Cause permanent harm to the intestines.

  • Lead to intestinal bleeding of the bowel.

  • Lead to a serious disease such as cancer.

It has not been shown to lead to serious, organic diseases, nor has a link been established between IBS and inflammatory bowel diseases such as Crohn's disease or ulcerative colitis.

What causes irritable bowel syndrome?

The digestion and propulsion of nutrients and fluids through the gastrointestinal system (GI) is a very complicated and very well-organized process. The GI tract has its own intrinsic muscles and nerves that connect, like an electrical circuit, to the spinal cord and brain. Neuromuscular events occurring in the GI tract are relayed to the brain through neural connections, and the response of the brain is also relayed back to the gastrointestinal tract. As a result of this activity, motility and sensation in the bowel are generated. An abnormality in this process results in a disordered propulsion of the intestinal contents, which generates the sensation of pain.

The exact cause of IBS is unknown. One theory is a person with IBS may have a colon that is more sensitive and reactive than usual, so it responds strongly to stimuli that would not affect others. The colon muscle of a person with IBS then begins to spasm after only mild stimulation or ordinary events such as the following:

  • Eating

  • Distention from gas or other material in the colon

  • Certain medications

  • Certain foods

Women with IBS seem to have more symptoms during their menstrual periods, suggesting that reproductive hormones can increase IBS symptoms.

What are triggers for IBS?

The most likely triggers for IBS are diet and emotional stress. Scientists have some clues as to why this happens. Consider the following:

  • Diet. Eating causes contractions of the colon, normally causing an urge to have a bowel movement within 30 to 60 minutes after a meal. Fat in the diet can cause contractions of the colon following a meal. With IBS, however, the urge may come sooner, accompanied by cramps and diarrhea.

  • Stress. Stress stimulates colonic spasm in people with IBS. Although not completely understood, it is believed to be because the colon is partly controlled by the nervous system. Counseling and stress reduction techniques can help relieve the symptoms of IBS; however, this does not mean IBS is the result of a personality disorder. It is at least partly a disorder of colon motility.

What are the symptoms of IBS?

The following are the most common symptoms of IBS. However, each individual may experience symptoms differently. Symptoms may include:

  • Crampy abdominal pain

  • Painful constipation and/or diarrhea.

  • Alternating constipation and diarrhea

  • Mucus may be in the bowel movement

Bleeding, fever, weight loss, and persistent, severe pain are not symptoms of IBS, but indicate other problems. The symptoms of IBS may resemble other medical conditions or problems. Always consult your doctor for a diagnosis.

How is irritable bowel syndrome diagnosed?

Your doctor will obtain a thorough medical history, perform a physical examination, and obtain screening laboratory tests to assess for infection and inflammation. More than likely, all the screening tests and physical examination will be normal. In most cases  IBS  is a diagnosis of exclusion. The laboratory tests, imaging studies, and procedures to be performed will be dictated by the history and physical examination. Tests and procedures that your doctor may order may include the following:

  • Blood tests. These are done to determine if you are anemic, have an infection, or have an illness caused by inflammation or irritation.

  • Urine analysis and culture. These are done to help diagnose urinary tract infections.

  • Stool culture. This checks for the presence of abnormal bacteria in the digestive tract that may cause diarrhea and other problems. A small sample of stool is collected and sent to a laboratory by your doctor's office. In two or three days, the test will show whether abnormal bacteria are present.

  • Fecal occult blood test. This checks for hidden (occult) blood in the stool. It involves placing a very small amount of stool on a special card, which is then tested in the doctor's office or sent to a laboratory. If blood is present, it may suggest an inflammatory source in the gastrointestinal tract.

  • Esophagogastroduodenoscopy (also called EGD or upper endoscopy). A procedure that allows the doctor to examine the inside of the esophagus, stomach, and duodenum (the first part of the small intestine where absorption of vitamins, minerals, and other nutrients begins). A thin, flexible, lighted tube, called an endoscope, is guided into the mouth and throat, then into the esophagus, stomach, and duodenum. The endoscope allows the doctor to view the inside of this area of the body, as well as to insert instruments through the scope for the removal of a sample of tissue for biopsy (if necessary).

  • Abdominal X-rays. A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film.

  • Abdominal ultrasound. A diagnostic imaging technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels. Gel is applied to the area of the body being studied, such as the abdomen, and a wand called a transducer is placed on the skin. The transducer sends sound waves into the body that bounce off organs and return to the ultrasound machine, producing an image on the monitor. A picture or video recording of the test is also made so it can be reviewed in the future.

  • Colonoscopy. A procedure that allows the doctor to view the entire length of the large intestine, and can often help identify abnormal growths, inflamed tissue, ulcers, and bleeding. It involves inserting a colonoscope, a long, flexible, lighted tube, in through the rectum up into the colon. The colonoscope allows the doctor to see the lining of the colon, remove tissue for further examination, and possibly treat some problems that are discovered.

What is the treatment for IBS?

Specific treatment for IBS will be determined by your doctor based on:

  • Your age, overall health, and medical history

  • Extent of the condition

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

Treatment may include:

  • Changes in diet. Eating a proper diet is important with irritable bowel syndrome. In some cases of IBS, a high-fiber diet can reduce the symptoms. Keeping a list of foods that cause distress, and discussing the findings with a doctor or registered dietitian, can help.

  • Medication. Doctors may prescribe fiber supplements or occasional laxatives. Some doctors prescribe a serotonin 5-HT3 antagonist (Lotronex), antispasmodic medications, tranquilizers, or antidepressants to relieve symptoms. Lotronex is usually prescribed for women with severe IBS who have not responded to conventional therapy.

What are good fiber sources?


Moderate fiber

High fiber


Whole wheat bread, granola bread, wheat bran muffins, Nutri-Grain waffles, popcorn



Bran Flakes, Raisin Bran, Shredded Wheat, Frosted Mini Wheats, oatmeal, Mueslix, granola, oat bran

All-Bran, Bran Buds, Corn Bran, Fiber One, 100% Bran


Beets, broccoli, brussels sprouts, cabbage, carrots, corn, green beans, green peas, acorn and butternut squash, spinach, potato with skin, avocado



Apples with peel, dates, papayas, mangos, nectarines, oranges, pears, kiwis, strawberries, applesauce, raspberries, blackberries, raisins

Cooked prunes, dried figs

Meat substitutes

Peanut butter, nuts

Baked beans, black-eyed peas, garbanzo beans, lima beans, pinto beans, kidney beans, chili with beans, trail mix