What is Small Intestine Bacterial Overgrowth (SIBO)

Small Intestine Bacterial Overgrowth (SIBO) is a clinical condition characterized by an excessive increase in the bacterial population within the small intestine, which typically results in digestive distress and nutrient malabsorption. Unlike the large intestine, the small intestine should host a relatively low number of bacteria; when this balance is disrupted, it leads to symptoms such as bloating, abdominal pain, and diarrhea.

What happens in the body during SIBO?

In a healthy digestive system, the small intestine is kept relatively clear of bacteria by the Migrating Motor Complex (MMC), a series of cleansing waves. When this motility is impaired—or if there is a structural blockage—bacteria from the large intestine can migrate upward or proliferate in the small intestine. Small Intestine Bacterial Overgrowth (SIBO) disrupts the normal digestive process by fermenting carbohydrates before the body can absorb them, producing excess gas and causing inflammation in the intestinal lining.

How is Small Intestine Bacterial Overgrowth classified?

Clinicians often classify Small Intestine Bacterial Overgrowth (SIBO) based on the type of gas produced during breath testing, which correlates with the specific type of overgrowth:

• Hydrogen-dominant SIBO: Typically associated with diarrhea and rapid transit.


• Methane-dominant SIBO (IMO): Often associated with chronic constipation and slower intestinal transit.


• Hydrogen Sulfide SIBO: A less common variant often linked to sensitivity to sulfur-rich foods.

Who is typically affected by SIBO?

Data on the exact prevalence of Small Intestine Bacterial Overgrowth (SIBO) is difficult to quantify due to varying diagnostic criteria, but it is frequently identified in patients with underlying conditions such as Irritable Bowel Syndrome (IBS), where studies suggest up to 30-60% of patients may test positive. It can affect individuals of all ages, though it is more frequently diagnosed in women and older adults, often appearing secondary to conditions like diabetes, scleroderma, or post-surgical changes in the gut.

What differentiates SIBO from other digestive issues?

Unlike standard food intolerances or general IBS, Small Intestine Bacterial Overgrowth (SIBO) is defined specifically by the location of the bacteria. While IBS is a diagnosis of exclusion, SIBO is a measurable physiological state that can be identified through standardized breath tests. Currently, 30 people with Small Intestine Bacterial Overgrowth (SIBO) have joined the DiseaseMaps community to share their experiences and navigate these complex symptoms together.

Next steps

• Consult a gastroenterologist regarding specialized breath testing (lactulose or glucose).


• Keep a detailed food and symptom diary to identify specific triggers.


• Join the DiseaseMaps community to connect with others managing this condition.


• Discuss prokinetic agents with your doctor to support gut motility and prevent recurrence.

Medical disclaimer: This content is for educational purposes only and does not constitute professional medical advice, diagnosis, or treatment; always seek the advice of your physician regarding a medical condition.

References

• NIH National Center for Advancing Translational Sciences (GARD)


• PubMed: "Small Intestinal Bacterial Overgrowth: A Comprehensive Review"


• The American College of Gastroenterology (ACG) Clinical Guidelines


• International Foundation for Gastrointestinal Disorders (IFFGD)