Irritable Bowel Syndrome may be linked to the presence of excessive bacteria in the small intestine

December 12, 2000

LOS ANGELES, Ca.- Researchers at Cedars-Sinai Medical Center may have identified the cause of Irritable Bowel Syndrome (IBS), a gastrointestinal condition that afflicts about 20 percent of the adult population and is diagnosed in twice as many women as men. The findings, published in the December issue of The American Journal of Gastroenterology, may shed new light on how to treat the symptoms of bloating, abdominal pain, diarrhea and/or constipation associated with IBS.

"Our research shows that the majority of patients we evaluated with IBS had excessive bacteria in the small intestine and that treatment with antibiotics greatly reduced the gastrointestinal symptoms of this condition," said Dr. Mark Pimentel, the principal investigator of the study and Assistant Director of the Cedars-Sinai GI Motility Program.

In the study, the investigators evaluated 202 patients who underwent a specialized breath test to determine the presence of small intestinal bacterial overgrowth (SIBO), a condition in which excessive quantities of bacteria are present in the small intestine. The researchers found that SIBO was present in 78 percent of the patients tested.

"The fact that SIBO was found in the majority of patients we tested with IBS suggests a strong association between the two conditions," said Dr. Pimentel.

To determine whether eliminating SIBO from the small intestine would improve the symptoms of IBS, patients who tested positive for excessive bacteria were subsequently treated with antibiotics for 10 days. Among these patients, 47 returned for a follow-up breath test approximately 10 days after they completed treatment with the prescribed antibiotic. The breath tests were subsequently analyzed for the presence of SIBO. The investigators found no SIBO present in 25 of these patients, while some SIBO was still detected in 22 of the patients as indicated by the breath test.

"On the whole, we found a significant reduction in the symptoms of IBS even in those patients in which SIBO was only partially eradicated," said Dr. Pimentel, noting that an alternative antibiotic may have been necessary to completely eliminate SIBO in these patients.

Among the 25 patients in which no SIBO was detected after treatment with antibiotics, 12 reported no symptoms of IBS whatsoever, while the symptoms of IBS were found to be significantly reduced in the remaining 13 patients.

The symptoms were also reduced in the patients in which some SIBO was still detected after completing the 10-day course of antibiotics, suggesting that treatment to the point in which SIBO was completely eliminated could have achieved better results.

"This is the first study to demonstrate that complete eradication of SIBO with commonly prescribed antibiotics substantially improves the symptoms of IBS, especially those associated with bloating, diarrhea and abdominal pain," said Dr. Henry C. Lin, senior author of the study and Director of the Cedars-Sinai GI Motility Program.

Currently, the investigators are conducting follow-up studies to determine how long some patients need to be treated to completely eliminate SIBO. To prevent patients from developing a resistance to antibiotics, the investigators plan to test novel non-antibiotic therapies in future clinical trials.
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Cedars-Sinai Medical Center is one of the largest and finest non-profit hospitals in the Western United States. For the fifth straight two-year period, Cedars-Sinai has been named Southern California's gold standard in healthcare in an independent survey. Cedars-Sinai is internationally renowned for its diagnostic and treatment capabilities and its broad spectrum of programs and services, as well as breakthrough biomedical research and superlative medical education. The Medical Center ranks among the top 12 non-university hospitals in the nation for its research activities.

To arrange a media interview, or for more information, please contact Kelli Stauning at 310-423-4767. Thank you.

Cedars-Sinai Medical Center

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