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Small Intestinal Bacterial Overgrowth

Small Intestinal Bacterial Overgrowth


Small intestinal bacterial overgrowth (SIBO) occurs when there is an abnormal increase in the overall bacterial population in the small intestine — particularly types of bacteria not commonly found in that part of the digestive tract. SIBO commonly results when a circumstance — such as surgery or disease — slows the passage of food and waste products in the digestive tract, creating a breeding ground for bacteria.

While SIBO is often a complication of stomach (abdominal) surgery, this condition can also result from structural problems and some diseases. Sometimes surgery is needed to correct the problem, but antibiotics are the most common treatment.

Why small intestinal bacterial overgrowth (SIBO) develops

The small intestine is the longest section of your digestive tract, measuring about 20 feet (6.1 meters). The small intestine is where food mixes with digestive juices and nutrients are absorbed into your bloodstream.

Unlike your large intestine (colon), your small intestine normally has relatively few bacteria due to rapid flow of contents and the presence of bile. But in SIBO, stagnant food in the bypassed small intestine becomes an ideal breeding ground for bacteria. The bacteria may produce toxins as well as interfere with the absorption of nutrients. The breakdown products following bacterial digestion of food can also trigger diarrhea.


Signs and symptoms of SIBO often includes:

  • Loss of appetite
  • Abdominal pain
  • Nausea
  • Bloating
  • An uncomfortable feeling of fullness after eating
  • Diarrhea
  • Unintentional weight loss
  • Malnutrition


Small intestinal bacterial overgrowth (SIBO) can be caused by:

  • Complications of abdominal surgery,including gastric bypass for obesity and surgeries to treat ulcers and abdominal cancers
  • Structural problems in and around your small intestine,including scar tissue (intestinal adhesions) and bulging pouches of tissue that protrude through the wall of the small intestine (intestinal diverticulosis)
  • Certain medical conditions,including Crohn’s disease, radiation enteritis, scleroderma, celiac disease, diabetes or other conditions that can slow movement (motility) of food and waste products through the small intestine.


Small intestinal bacterial overgrowth (SIBO) can cause escalating problems, including:

  • Poor absorption of nutrients:This can result in diarrhea, malnutrition and weight loss.
  • Vitamin deficiency:As a result of incomplete absorption of fats, your body can’t fully absorb the fat-soluble vitamins A, D, E and K. The overgrowth of bacteria can result in B-12 deficiency that can lead to weakness, fatigue, tingling, and numbness in your hands and feet.
  • Weakened bones (osteoporosis):This is due to poor calcium absorption
  • Kidney stones:Poor calcium absorption may also eventually result in kidney stones.

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