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DigestiveICD-10: K63.89Estimated to affect up to 15-20% of the general population, higher among IBS patients

Small Intestinal Bacterial Overgrowth (SIBO)

Small intestinal bacterial overgrowth (SIBO) is a condition in which excessive amounts of bacteria colonize the small intestine, leading to digestive symptoms and malabsorption of nutrients. Normally, the small intestine has relatively few bacteria compared to the large intestine, and SIBO disrupts this balance. SIBO is increasingly recognized as an underlying cause of irritable bowel syndrome (IBS) symptoms and can result in nutritional deficiencies if left untreated.

Symptoms

Abdominal bloating and distension, especially after meals
Excess gas and flatulence
Abdominal pain and cramping
Diarrhea, constipation, or alternating between both
Nausea and feeling of fullness
Unintended weight loss
Fatigue and brain fog from nutrient malabsorption
Fatty stools (steatorrhea)

Causes

  • Impaired small intestine motility due to conditions like diabetes, scleroderma, or hypothyroidism
  • Structural abnormalities such as intestinal strictures, adhesions, or surgical blind loops
  • Reduced stomach acid production from proton pump inhibitor use or atrophic gastritis
  • Immune deficiency or dysfunction affecting gut defense mechanisms
  • Ileocecal valve dysfunction allowing backflow from the colon

Risk Factors

  • Use of proton pump inhibitors or other acid-suppressing medications
  • History of abdominal surgery
  • Diabetes mellitus with associated gastroparesis
  • Irritable bowel syndrome (IBS)
  • Chronic pancreatitis or liver cirrhosis
  • Advanced age
  • Hypothyroidism

Diagnosis

  • Lactulose or glucose hydrogen/methane breath test
  • Small bowel aspirate and culture (gold standard but invasive)
  • Blood tests to evaluate vitamin B12, iron, and folate levels
  • Comprehensive metabolic panel to assess nutritional status

Treatment

  • Antibiotic therapy (rifaximin) targeted at gut bacteria
  • Elemental diet as an alternative to antibiotics for 2-3 weeks
  • Prokinetic medications to improve small intestine motility
  • Dietary modifications such as the low-FODMAP diet to reduce symptoms
  • Correction of nutritional deficiencies (B12, iron, fat-soluble vitamins)
  • Treatment of underlying conditions contributing to SIBO

Prevention

  • Avoid unnecessary long-term use of proton pump inhibitors
  • Manage underlying conditions such as diabetes and hypothyroidism
  • Eat at regular intervals and avoid frequent snacking to support the migrating motor complex
  • Stay physically active to promote healthy gut motility
  • Work with a healthcare provider to address any structural issues post-surgery

When to See a Doctor

  • Chronic bloating, gas, and abdominal discomfort persist despite dietary changes
  • You experience unexplained weight loss or signs of nutritional deficiency
  • Symptoms of IBS do not improve with standard treatment

Frequently Asked Questions

Related Conditions

Acid Reflux (Heartburn)

Digestive

Hypothyroidism

Endocrine

Type 2 Diabetes

Endocrine

Anemia

Metabolic

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

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