Irritable Bowel Syndrome - Diagnosis

How was the diagnosis of your irritable bowel syndrome established?

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How is irritable bowel syndrome (IBS) diagnosed?

The Rome Criteria

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.

Exclusion of non-functional gastrointestinal disease

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.

Exclusion of non-intestinal disease

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.

Evaluation of intestinal transportation

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.

Psychiatric illness

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.

Return to Irritable Bowel Syndrome (IBS)

See what others are saying

Comment from: Miller, 35-44 Female (Patient) Published: April 14

After several MRIs, Barium tests, X-Rays, and ultrasounds (including a gynecological ultrasound), I was told I had irritable bowel syndrome (IBS). I have had it now for three years and never get relief. I have had a chronic stomach ache since then. I go from diarrhea to constipation (hospitalized for three days once as I was full of poop). I always have a stomach ache. I am usually bloated, tired, and fearful of travelling. I cannot play with my kids properly. I have been given no real medication to try. I have been taking Metamucil and laxatives for a year now. I also have sharp pain in my right side, and I cannot sleep on any side any longer. I feel like I am being poked by something on my right side. I had my gallbladder removed seven years ago, and they think that is scar tissue. I wish someone could figure this thing out!

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Comment from: Positive, 19-24 Female (Patient) Published: February 28

I was diagnosed with IBS (irritable bowel syndrome) today after the doctor did a colonoscopy a week ago. It has been 1 year and 2 months that I have been struggling with pain going in and out of hospital.

Was this comment helpful?Yes


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