1. Irritable Bowel Syndrome (IBS) Slideshow Pictures
2. Digestive Disease Myths Slideshow Pictures
3. Diverticulitis (Diverticulosis) Slideshow Pictures

Medical Author:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Medical Editor:

Bhupinder Anand, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Irritable bowel syndrome (IBS) facts
• What is irritable bowel syndrome (IBS)?
• What causes irritable bowel syndrome (IBS)?
• What are symptoms of irritable bowel syndrome (IBS)?
• What are the complications of irritable bowel syndrome (IBS)?
• How is irritable bowel syndrome (IBS) diagnosed?
• How is irritable bowel syndrome (IBS) treated?
• Constipation medications
• Diarrhea medications
• Abdominal pain medications
• Psychotropic drugs
• Psychological treatments
• IBS Diet
• Is there a relationship between IBS and small intestinal bacterial overgrowth?
• What is a reasonable approach to irritable bowel syndrome (IBS)?
• What is in the future for irritable bowel syndrome (IBS)?
• Patient Comments: Irritable Bowel Syndrome - Diagnosis
• Patient Comments: Irritable Bowel Syndrome (IBS) - Treatments
• Patient Comments: Irritable Bowel Syndrome (IBS) - Symptoms
• Find a local Gastroenterologist in your town
• Irritable Bowel Syndrome Index

The complications of functional diseases of the gastrointestinal tract are relatively limited. Since the symptoms are often provoked by eating, patients who alter their diets and reduce their intake of calories may lose weight. Fortunately, loss of weight is unusual in functional diseases, and it should suggest the presence of a non-functional disease. Symptoms that awaken patients from sleep also are more likely to be due to non-functional than functional diseases.

Most commonly, functional diseases interfere with the patients' comfort and daily activities. For example, patients who suffer from morning diarrhea may not leave their home until the diarrhea stops. If the diarrhea is constant, they may go only to places where they know that a toilet is readily available. Patients who develop pain after eating may skip lunch. Very commonly, patients associate symptoms with specific foods, such as milk, fat, vegetables, etc. Whether or not such associations are real, these patients will restrict their diets accordingly. Milk is the food that is most commonly eliminated, often unnecessarily and to the detriment of adequate calcium intake. The interference with daily activities also can lead to problems with interpersonal relationships, especially with spouses. However, most patients with functional disease tend to just live with their symptoms and only infrequently visit physicians for diagnosis and treatment.

The symptoms of IBS are varied and inconsistent among patients. Moreover, there are no characteristically abnormal tests that can be used to diagnose IBS. All of this has made it difficult to define IBS and identify patients, especially for research studies. In 1992, a group of international investigators of gastrointestinal diseases met in Rome and developed a set of criteria to be used for diagnosing IBS. The criteria were modified in 1999 and again in 2006. These three sets of criteria are known as the Rome, I, II, and III criteria.

The the most recent criteria, the Rome III criteria state that in order to be diagnosed with IBS, a patient should have abdominal discomfort or discomfort (not described as pain) at least once weekly for at least two months. The discomfort should be associated with two out of three of the following features:

• Relief with a bowel movement
• Onset associated with a change in the frequency of bowel movement
• Onset associated with a change in the form (appearance) of stool

There should be no evidence of an inflammatory, anatomic (obstructive), metabolic, or neoplastic (tumorous) cause of the symptoms.

Symptoms of dyspepsia (defined by Rome III criteria as abdominal discomfort or pain in the upper abdomen), abdominal distention, and increased flatus (passing gas, or flatulence) do not fall within this definition. Nevertheless, many patients have these symptoms along with the symptoms of IBS. It is not clear if these patients have one problem (IBS) or more than one problem.

As mentioned previously, the exclusion of non-functional disease in patients with suspected IBS is an important concern. There are many tests designed to exclude non-functional diseases. The primary issue, however, is to decide which tests are reasonable to perform. Tests are selected individually since each case different. Nevertheless, there are some basic tests that are often performed to exclude non-functional gastrointestinal disease. These tests identify anatomic (structural) and histological (microscopic) diseases of the intestines.

• As always, a detailed history from the patient and a physical examination frequently will suggest the cause of the symptoms.
• Routine screening blood tests are performed looking for clues to unsuspected diseases.
• Examination of stool also is a part of the evaluation since it may reveal infection, signs of inflammation, or blood and direct further diagnostic testing. Sensitive stool testing (antigen/antibody) for Giardia lamblia would be reasonable because this parasitic infection is common and can be acute or chronic.
• Some physicians do blood testing for celiac disease (sprue), but the value of doing this is unclear. Moreover, if an EGD is planned, biopsies (taking samples of tissue) of the duodenum usually will make the diagnosis of celiac disease.
• Both X-rays and endoscopies can identify anatomic diseases. Only endoscopies, however, can diagnose histological diseases because biopsies can be taken during the procedure. The X-ray tests include:
  • The esophagram and video-fluoroscopic swallowing study to examine the esophagus
  • The upper gastrointestinal series to examine the stomach and duodenum
  • The small bowel series to examine the small intestine
  • The barium enema to examine the colon and terminal ileum.

The endoscopic tests include:

• Upper gastrointestinal endoscopy (esophago-gastro-duodenoscopy, or EGD) to examine the esophagus, stomach, and duodenum
• Colonoscopy to examine the colon and terminal ileum
• Endoscopy also is available to examine the small intestine, but this type of endoscopy is complex, not widely available, and of unproven value in suspected IBS.

For examination of the small intestine, there is also a capsule containing a tiny camera that can be swallowed (capsule endoscopy). As the capsule travels through the intestines, it sends pictures of the inside of the intestines to an external recorder for later review. However, the capsule is not widely available and its value in IBS has not yet been proven.

X-rays are easier to perform and are less costly than endoscopies. The skills necessary to perform X-rays, however, are becoming rarer among radiologists because they are doing them less often. Therefore, the quality of the X-rays often is not as high as it used to be. As noted above, endoscopies have an advantage over X-rays because at the time of endoscopies, biopsies can be taken to diagnose or exclude histological diseases, something that X-rays cannot do.

Patients with suspected IBS often undergo abdominal ultrasonography (US), computerized tomography (CT or CAT scans), or magnetic resonance imaging (MRI). These tests are used primarily to diagnose non-intestinal diseases. (Although these tests also may diagnose intestinal diseases, their value for this purpose is limited. As described above, X-ray and endoscopy are better tests.) It also is important to realize that US, CT, and MRI are powerful tests and will uncover abnormalities that are unrelated to IBS. The most common example is the finding of gallstones that, in fact, often cause no symptoms. This finding can cause a problem if the gallstones are assumed to be the source of the IBS symptoms. The problem is that surgical removal of the gallbladder with its gallstones (cholecystectomy) is unlikely to relieve the symptoms of IBS. (Cholecystectomy would be expected to relieve only the characteristic symptoms that gallstones sometimes can cause.) Tests to exclude non-intestinal diseases may be appropriate in specific situations, although certainly not in most patients.

If abnormal function of the muscles of the small intestine is suspected, tests to evaluate transportation through the small intestine or the colon (small intestinal and colonic transit studies, respectively) are available. These studies are done with either radioactive compounds or markers that can be seen on X-rays of the abdomen. It also is possible to pass catheters into the stomach and small intestine or the colon to determine if the muscles of these organs are working normally (antro-duodenal and colonic motility studies, respectively). Finally, constipation due to malfunction of the anal muscles can be diagnosed by ano-rectal motility studies.

The possibility of a psychiatric (psychosomatic) illness often arises in patients with IBS because the symptoms frequently are subjective, and no objective abnormalities can be identified. Psychiatric illness may complicate IBS, but it is unclear if psychiatric illness causes IBS. If there is a possibility of psychiatric illness, a psychiatric evaluation is appropriate.