Small Intestinal Bacterial Overgrowth (SIBO)

SIBO is an overgrowth of bacteria in the small intestine, where bacterial counts are normally low. It can cause bloating, gas, abdominal discomfort, and nutrient malabsorption.

Table of Contents

Quick Facts

  • ICD-10: K90.9

Symptoms

  • Bloating, often worse after meals
  • Excessive gas
  • Abdominal pain or discomfort
  • Diarrhea or constipation
  • Unintended weight loss
  • Vitamin B12 deficiency
  • Fatigue

Causes

  • Reduced intestinal motility (diabetes, scleroderma)
  • Anatomical changes (surgical, strictures, diverticula)
  • Low stomach acid (chronic PPI use)
  • Immune deficiency
  • Chronic pancreatitis

Diagnosis

  • Breath testing (hydrogen, methane)
  • Small bowel aspirate culture (gold standard but invasive)
  • Clinical response to treatment

Treatment

  • Antibiotics (rifaximin most common)
  • Address underlying motility or anatomical issues
  • Dietary modification (low-FODMAP, elemental diets)
  • Probiotics — variable evidence
  • Repeat treatment for recurrence

Related Conditions

IBS

Overlaps with SIBO

 Bloating

Common symptom
Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about a medical condition. If you are experiencing a medical emergency, call your local emergency number immediately.

References

  • American College of Gastroenterology. SIBO Clinical Guidelines.