What is SIBO?
Small Intestinal Bacterial Overgrowth (SIBO) is a condition where excessive bacteria colonize the small intestine, leading to symptoms like bloating, abdominal pain, diarrhea, constipation, and nutrient malabsorption. It’s often misdiagnosed as irritable bowel syndrome (IBS) because of overlapping symptoms. Metabolic Solutions has decades of experience providing this testing for leading clinicians at the Mayo Clinic and many other GI leaders.
Why SIBO Is Underdiagnosed
SIBO remains significantly underdiagnosed due to overlapping symptoms, limited clinician awareness, imperfect diagnostic tools, and systemic gaps between research and clinical practice.
Overlapping Symptoms with IBS and Other GI Disorders
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- Symptoms like bloating, abdominal pain, gas, diarrhea, and constipation are common in both SIBO and irritable bowel syndrome (IBS), leading to misdiagnosis.
- IBS is often considered a 'wastebasket diagnosis,' masking underlying SIBO.
- Studies show that approximately one in three IBS patients actually have SIBO.
Limited Awareness Among Clinicians
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- Many gastroenterologists and primary care providers lack familiarity with SIBO, delaying testing and recognition.
- SIBO was initially recognized in naturopathic circles, and conventional medicine adoption has been slow.
Under-recognition of Underlying Risk Factors
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- Risk factors like motility disorders, gastric acid suppression, structural anomalies, and immunodeficiency are often overlooked.
Research–Clinical Implementation Disconnect
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- Despite evidence linking SIBO to IBS, clinical testing adoption remains limited.
Importance of Breath Testing in Differential Diagnosis of SIBO
Breath testing plays a critical role in the differential diagnosis of SIBO for several key reasons:
Non-Invasive, Accessible & Safe
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- Jejunal aspirates for bacterial culture—the diagnostic gold standard—are invasive and expensive. Breath tests are simple, non-invasive, and widely available.
Differentiates SIBO from Other GI Disorders
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- Symptoms of SIBO overlap with IBS and other conditions. Breath tests detect excess bacterial fermentation, helping distinguish SIBO from functional disorders.
Measures Hydrogen & Methane for Subtype Classification
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- Breath patterns help identify hydrogen-predominant SIBO (linked to diarrhea) and methane-predominant SIBO/IMO (linked to constipation), guiding targeted treatment.
Guides Treatment & Monitors Response
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- Breath testing confirms SIBO before treatment, monitors effectiveness, and detects relapse if symptoms return.
Standardized Criteria Inform Accuracy
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- Consensus thresholds (e.g., hydrogen rise ≥20 ppm within 90 minutes or methane ≥10 ppm) improve diagnostic reliability.
- Breath tests rely on indirect measurements and can be influenced by gut transit time and patient preparation. Awareness of these factors ensures accurate interpretation.
Glucose vs. Lactulose: Choosing the Right Testing Substrate for SIBO
At Metabolic Solutions, we provide two versions of the Small Intestinal Bacterial Overgrowth (SIBO) breath test. Both tests follow the same protocol, but they differ in one key aspect—the substrate used to challenge the small intestine.
Clinicians select between glucose and lactulose based on specific diagnostic goals. Here’s a simplified guide:
- Glucose is typically preferred when high specificity is required, particularly for detecting proximal SIBO. Because glucose is rapidly absorbed in the upper small intestine, an early rise in hydrogen or methane strongly suggests bacterial fermentation in this region.
- Lactulose, on the other hand, is favored when assessing distal SIBO or evaluating intestinal motility. Unlike glucose, lactulose is not absorbed and travels through the entire small intestine, making it useful for detecting overgrowth further downstream.
- Both substrates provide valuable insights into the presence or absence of bacterial overgrowth in the small intestine, but the choice often depends on the clinical question at hand.
Treatment and Follow-Up Testing
- Antibiotics for SIBO: Rifaximin for hydrogen-dominant SIBO; rifaximin + neomycin for methane-dominant cases.
- Dietary strategies: Low-FODMAP diet, elemental diet.
- Prokinetics and probiotics: Support gut motility and microbiome balance.
- Follow-up: Symptom-based; retesting if symptoms persist.
Key Takeaways
SIBO is a complex condition requiring accurate diagnosis and tailored treatment. Understanding breath test limitations, choosing the right antibiotic regimen, and supporting gut health through diet and lifestyle are essential for long-term management.