August 29th, 2012
SIBO (small intestinal bacterial overgrowth): How common is it, and how should we diagnose it?
Our hospital used to provide hydrogen breath testing for the community but recently discontinued this practice. I was asked to comment on whether it should be discontinued and how often I used the test. It surprised me that I had not ordered a hydrogen breath test in the 2 decades I have been here but that many docs did. Although all of us are aware that small intestinal bacterial overgrowth can occur (e.g., scleroderma-type bowel motility disorders, post-operative blind loops, etc.), it seems that this diagnosis is being made more often in otherwise normal people without an obvious etiology.
So the conversation I want to generate is the following:
1) How often do you entertain a diagnosis of SIBO, and what symptoms/settings make you consider the diagnosis?
2) Do you think SIBO is being overdiagnosed or underdiagnosed?
3) If you consider SIBO, do you do a diagnostic test, and, if so, which one?
4) Given that no test for SIBO is validated against a gold-standard diagnosis, how do you chose the test you are using?
5) If you do not test for bacterial overgrowth, do you treat empirically, and, if so, with what?
6) What test characteristics do you want to see before you would use a test for bacterial overgrowth?
I look forward to the conversation!
5 Responses to “SIBO (small intestinal bacterial overgrowth): How common is it, and how should we diagnose it?”
M. Brian Fennerty, MD
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NEJM Journal Watch Gastroenterology
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Dear Dr. Fennerty,
I work closely with Dr. Mark Pimentel and have published his first book, “A New IBS Solution” which has turned into the Bible of all SIBO Books on the market.
I thought Dr. Pimentel’s answers might be helpul to you and your readers.
As you may be aware, Dr. Pimentel is the Director of the GI Motility Program at Cedars-Sinai Medical Center and is one of the Pioneers in diagnosing/Treating SIBO.
Please feel free to contact me with any questions.
Best,
David Knight
1) How often do you entertain a diagnosis of SIBO and what symptoms/settings make you consider the diagnosis?
If someone has post-prandial bloating, I think of SIBO. Most IBS patient are now SIBO based on recent culture data showing SIBO in 60% of D-IBS.
2) Do you think SIBO is being over-diagnosed or under-diagnosed?
I think it is being underdiagnosed and recent culture studies as I allude to above support that.
3) If you consider SIBO, do you do a diagnostic test and if yes, which one?
While the lactulose breath test tends to overcall SIBO (80% of IBS test positive), this is closer to the culture data than glucose breath testing which is only positive in 30%. Glucose is absorbed so quickly it has a high specificity but low sensitivity.
4) As no test for SIBO is validated against a gold-standard diagnosis, how do you chose the test you are using?
The problem is that even culture is not validated. In a systematic review that we published on this whole area of diagnostic tests in SIBO, we found that >105 per mL is only seen in Billroth II and antrectomized patients. If you use healthy as a control, anything over 1000 coliforms/mL is SIBO. So this whole area was a mess until recently.
5) If you do not test for bacterial overgrowth, do you treat empirically and if so, with what?
Since SIBO is so common, we tend to be more empiric lately with IBS patients.
6) What test characteristics do you want to see before you would use a test for bacterial overgrowth?
We do breath testing if constipated because if methane is present, we have to give neomycin plus rifaximin for treatment as neither alone is very effective in this subset.
Hope this answered your questions.
Dr. Mark Pimentel-Director GI Motility Program Cedars-Sinai Medical Center
I am glad that Dr. Pimentel has chimed in on this topic, since his work has brought SIBO to the forefront of the IBS literature.
I treat patients with gas/bloat IBS with “anti gas” behavioral measures +/- probiotics or rifaximin, the latter mainly because of his work. However, as with all IBS therapies, the NNT is high and the placebo effect is astounding.
The test characteristics of breath testing are poor and I do not use it. I am hoping that a more reliable test for SIBO will be available soon – maybe a modification of the small bowel capsule that allows bacterial capture/titer estimation?
Hi iv have trouble or about 5 years with Ibs yes I old like the breath test . Iv got bloating
I have recently had a lactulose breath test. The result was negative. I have IBS – C.
However I was on a low FODMAP diet for 2 weeks before the breath test…could this have fudged the results?
Kind regards.
There is an obvious cause of SIBO that has been overlooked in medicine. Ever since the depression, the American diet has become increasingly laden with cheap omega-6 polyunsaturated oils. Even when our economic situation improved, the public did not go back to butter and animal fat because they were sold on the false idea that vegetable oils were healthy and saturated fat was harmful. A study by Sanjoy Ghosh with mice showed that a diet rich in omega-6 fatty acids disrupted the flora, caused inflammation, and caused bacterial overgrowth in the last part of the small intestine. Thus, SIBO has probably been making its insidious way into our society for a long time.
Reference for Polyunsaturated oils causing SIBO in mice:
“Diets rich in n-6 PUFA induce intestinal microbial dysbiosis in aged mice,” Sanjoy Ghosh, Erin Molcan, et al., British Journal of Nutrition, Published online January 2013. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8802149
Also see this article:
http://life.nationalpost.com/2013/01/23/excessive-omega-fatty-acids-may-make-heart-health-worse-not-better-b-c-researchers/