SIBO

I completed a round of the following tests with my functional medicine doctor:

1. Blood test to check for parasites
2. Breath test
3. GI stool comprehensive profile

TL;DR: It's clear that I have Small Intestinal Bacteria Overgrowth (SIBO), which is a subset of IBS. Remember that IBS is just a catch-all for chronic GI symptoms since we still have little understanding of this area.

SIBO is when there is an overgrowth of bacteria in your small intestine, where there should be minimal bacteria due to the stomach acids present. The way SIBO is detected is with a breath test, which measures the content of hydrogen or methane present in a breath sample at baseline, then the values after ingestion of a sugar solution (lactulose). Only bacteria produce hydrogen and methane so if there are elevated gases, then SIBO is present.

A normal result would have <20 ppm rise in hydrogen over time and <10 ppm of methane at all. My results show elevated methane gas, which is produced by methanogens (archaea). The low levels of hydrogen may be a false negative as methanogens consume hydrogen molecules. For example, if I did not have any methanogens, the chart below may show elevated levels of hydrogen.

The blood check came out negative. I did not have IgG antigens for certain parasites.

The stool test (which tests for bacteria DNA by PCR) was interesting. I have above normal levels of Bacteriodes vulgatus, Barnesiella, and Odoribacter, which are hydrogen-producing bacteria. I also had elevated levels of Methanobrevibacter smithii, a methane-producing archaea, which correlates with the breath test result.

So, what next?

Hydrogen-dominant SIBO is generally associated with IBS-D (D for diarrhea dominant symptoms). Methane-dominant SIBO is generally associated with IBS-C (for constipation). It's strange though because my IBS is D, although I have methane-dominant SIBO. I might have elevated methane and hydrogen, or even hydrogen sulfide, which there are no ways to clinically measure yet.

Most GI doctors prescribe Xifaxan (Rifaximin) for IBS-D as it is an approved antibiotic for treatment of IBS-D. It's actually well tolerated, isn't absorbed in the body, and works great for most people with IBS-D. I have history with taking Xifaxan - actually 3 prescriptions in the past. Once around 2013 after my initial IBS diagnosis, then around 2017 for IBS-D again but from a different GI doctor, and a 3rd time during the pre-treatment for FMT in a clinical trial for IBS-D. All three times I felt no change, which now makes sense as I have a methane-dominant SIBO.

I was just prescribed Flagyl (metronidazole) in combination with Xifaxan. I have experience with Flagyl, too! Back in 2017 I got sick in Vietnam and the doctor there gave me Flagyl to rid me of what they thought was a bacterial infection. I actually had HepA (and potentially a bacterial infection too). Flagyl did wonders on my belly and overall health. I felt amazing for 2-3 months after Flagyl and had no IBS symptoms. But then I relapsed.

The relapse is what I'm afraid of happening this time, but I have more tools to work on preventing that. Updates to come!