sibo
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Bacteria colonizing the wrong part of the gut — causing symptoms that look exactly like active celiac disease, and often persisting alongside it.
The small intestine normally contains relatively few bacteria compared to the large intestine. Small intestinal bacterial overgrowth (SIBO) occurs when bacteria (usually colonic species) colonize the small intestine in abnormal numbers. The resulting fermentation of carbohydrates produces gas and organic acids, causing bloating, diarrhea, and malabsorption — symptoms that are essentially indistinguishable from active celiac disease.
Connection to Celiac Disease
SIBO and celiac disease have a bidirectional relationship:
- SIBO as a consequence of celiac — intestinal damage alters gut motility and immune defenses, creating conditions favorable to bacterial overgrowth
- SIBO as a cause of NRCD — SIBO is the most common identifiable cause (after unintentional gluten ingestion) of non-responsive celiac disease
- SIBO persists independently — treating celiac (via GFD) does not treat SIBO; it requires its own intervention
Symptoms Overlap
Both SIBO and active celiac cause:
- Bloating, gas, abdominal distension
- Diarrhea (sometimes alternating with constipation)
- malabsorption of fats, vitamins
- Weight loss, fatigue
The distinction matters because treatment is different. Continuing to tighten GFD adherence won't resolve SIBO.
Diagnosis
- Hydrogen breath test — measures hydrogen/methane produced by bacterial fermentation of a test sugar (lactulose or glucose); elevated = SIBO
- Small intestinal aspirate — gold standard but invasive; direct bacterial culture
Treatment
- Rifaximin — non-absorbable antibiotic; first-line treatment; targets gut bacteria without systemic absorption
- Dietary modification (low-FODMAP, low-fermentable carbohydrate) — reduces substrate for bacterial fermentation
- Address underlying motility or anatomical issues if present
SIBO in the NRCD Workup
When a celiac patient on a strict GFD still has symptoms, SIBO should be among the first things investigated — it's common, treatable, and often missed because its symptoms are attributed to ongoing celiac activity. See non-responsive-celiac.
Related Concepts
non-responsive-celiac | malabsorption | gluten-free-diet | villous-atrophy | ncgs