Small Intestinal Bacterial Overgrowth (cont.)

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Is there a relationship between SIBO and irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) is a common gastrointestinal condition. Patients with IBS typically complain of abdominal pain associated with bloating, gaseousness, and alterations in their bowel habit (diarrhea, constipation, alternating diarrhea and constipation, or a sense of incomplete evacuation of stool). IBS is a chronic condition. Symptoms can be continuous or vary over months, years, or even decades. While irritable bowel syndrome is not life-threatening, symptoms of irritable bowel syndrome can have a major impact on a person's quality of life and even can be debilitating. For example, a patient with diarrhea after meals may avoid eating out. Patients who experience bloating and abdominal pain after meals may develop a fear of eating. In its extreme, they may even lose weight. Even flatulence can be socially limiting.

Irritable bowel syndrome has been a frustrating condition for both physicians and patients because it is difficult to diagnose and treat. Irritable bowel syndrome is difficult to diagnose because there is no diagnostic test that is abnormal. The diagnosis is made on the basis of typical symptoms and tests that exclude OTHER diseases that might be causing the symptoms such as ulcers, infections, tissue inflammation, cancers, and obstruction of the intestine. Tests to rule out other conditions include CT scans, barium X-rays, upper gastrointestinal endoscopies, and colonoscopies. Physicians have to rely heavily on their clinical judgment to decide when enough testing has been done and to confidently make a diagnosis of IBS. Physicians are frustrated further by the fact that the treatment for IBS is not helpful in many patients.

There is a striking similarity between the symptoms of IBS and SIBO. It has been theorized that SIBO may be responsible for the symptoms of at least some patients with irritable bowel syndrome. The estimates run as high as 50% of patients with irritable bowel syndrome. Support for the SIBO theory of IBS comes from the observation that many patients with IBS are found to have an abnormal hydrogen breath test, and some patients with irritable bowel syndrome have improvement of their symptoms after treatment with antibiotics, the primary treatment for SIBO. Furthermore, it has been reported that successful treatment of symptoms with antibiotics causes the hydrogen breath test to revert to normal, suggesting that bacteria indeed are causing the symptoms. Although this theory is tantalizing and there is much anecdotal information that supports it, the rigorous scientific studies that are necessary to prove the theory have just begun. Nevertheless, many physicians have already begun to treat patients with IBS for SIBO. The intriguing issue yet to be elucidated is the reason why individuals who appear to have normal small intestines develop SIBO and IBS. The most popular theory is that patients with IBS have a subtle abnormality in the function of their intestinal muscles that allows SIBO to occur. Another theory is that there is an immunologic defect that allows colonic bacteria to live in the small intestine.

Medically Reviewed by a Doctor on 3/10/2014

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Small Intestinal Bacterial Overgrowth - Symptoms Question: Please describe the symptoms and treatment of your small intestinal bacterial overgrowth.
Small Intestinal Bacterial Overgrowth - Causes Question: What was the cause of your intestinal bacterial overgrowth?
Small Intestinal Bacterial Overgrowth - Experience Question: Please describe your experience with small intestinal bacterial overgrowth (SIBO).
Small Intestinal Bacterial Overgrowth - IBS Question: If you've been tested for or diagnosed with SIBO, has IBS also been considered? Please share your experience.