SIBO Diagnosis
Content
1. Overview SIBO Diagnosis
2. Test sugars
3. Principle behind Breath Testing
4. Treatment Options
5. Differential Diagnoses
1. Overview SIBO Diagnosis
SIBO is typically diagnosed using a breath test. While the gold standard for diagnosis would be obtaining samples directly from the small intestine via endoscopy, this method is invasive, not widely available, and costly. Therefore, in clinical practice, the breath test is the preferred diagnostic tool.
2. Test sugars
Several different test substances can be used for the breath test, each with its own advantages and limitations. The most common substrates are lactulose, lactose, glucose, and fructose (1). These are ingested in liquid form as part of the test. The use of multiple substrates is necessary because not all bacteria metabolize every type of sugar.
Lactose, glucose, and fructose are naturally occurring sugars, whereas lactulose is a synthetic sugar that is barely absorbed by the human body. Since lactulose is not taken up by intestinal cells, it remains available in the gut as a prebiotic, serving as food for bacteria. If bacteria (particularly those in the small intestine) metabolize these sugars, they produce gases that can be measured in breath samples.
3. Principle behind Breath Testing
The breath test is based on the principle that human cells do not produce hydrogen or methane. Any increase in these gases after carbohydrate ingestion must originate from bacterial fermentation. The gases enter the bloodstream and are eventually exhaled, allowing their levels to be measured.
4. Treatment Options
If a SIBO diagnosis is confirmed, several treatment options are available. These include a specialized SIBO diet, herbal or conventional antibiotics (2), and probiotics. Treatment is tailored based on the type and severity of symptoms, as well as the predominant bacterial strains present.
5. Differential Diagnoses
Several conditions can present with symptoms similar to SIBO, including pancreatitis, exocrine pancreatic insufficiency, Crohn’s disease, ulcerative colitis, SIFO (small intestinal fungal overgrowth), and irritable bowel syndrome (IBS). This list is not exhaustive, and all potential differential diagnoses should be ruled out before starting SIBO treatment.
References
- Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, Schmulson M, Valdovinos M, Zakko S, Pimentel M. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017 May;112(5):775-784. doi: 10.1038/ajg.2017.46. Epub 2017 Mar 21. PMID: 28323273; PMCID: PMC5418558.
- Ginnebaugh B, Chey WD, Saad R. Small Intestinal Bacterial Overgrowth: How to Diagnose and Treat (and Then Treat Again). Gastroenterol Clin North Am. 2020 Sep;49(3):571-587. doi: 10.1016/j.gtc.2020.04.010. Epub 2020 Jun 14. PMID: 32718571.
