Small Intestine Bacterial Overgrowth
(SIBO; Small Bowel Bacterial Overgrowth; SBBO)
Definition
Bacteria normally exists in the intestines. It plays a role in digestion and overall health. Small intestine bacterial overgrowth (SIBO) is when there is too much bacteria in the small intestine.
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Causes TOP
SIBO is often caused by a problem with the small intestine. Damage or defects to the intestine may slow the flow of food. The slowed food may encourage the increased growth of bacteria. Problems of the intestine may be caused by:
- Birth defect
- Injury
- Surgery
- Digestive disorders
Risk Factors TOP
Any condition that affects how food moves through the intestines may increase the risk of SIBO. Some problems are:
- Crohn disease
- Irritable bowel syndrome (IBS)
- Short bowel syndrome
- Diverticulitis
- Intestinal stricture (narrowing in the small intestine)
- Digestive disorders, such as celiac disease or lactose intolerance
- A pancreas that is not making enough of the enzymes needed to break down food
- Blind loop syndrome (when part of the intestine is bypassed)
- Intestinal infections, such as food poisoning or traveler’s diarrhea
- Cirrhosis
- Diabetes
- Chronic pancreatitis
- End-stage kidney or liver disease
This problem is also more common in older adults. Other risk factors are:
- Prior intestinal surgery
- An obstruction in the small intestine
- Having a weakened immune system
Symptoms TOP
Problems may be:
- Belly pain
- Bloating and gas
- A feeling of fullness
- Constipation or diarrhea
- Weight loss
Diagnosis TOP
The doctor will ask about your symptoms and health history. A physical exam will be done.
Tests may include:
- Blood tests
- Breath tests—to look for certain gases after fasting and eating specific sugars
- Culture of intestinal fluid—a sample of fluid from the small bowel will be taken to see what bacteria is present
Treatment TOP
Any underlying health problems will need to be treated. The goal of treatment is to lower the levels of harmful bacteria.
Medications
Antibiotics are often used to treat SIBO. Usually treatment is temporary. Some may need to take antibiotics for a longer period.
Nutritional Support
Proper nutrients can help bring back the balance of bacteria. Steps that may help are:
- Working with a dietitian
- Following a special diet, such as a carbohydrate-restricted diet
- Taking vitamins and/or supplements
- Taking probiotics
Some people may need tube feeding with a special formula.
Surgery TOP
Surgery may be needed for severe SIBO. It may be done to correct a problem in the small bowel.
RESOURCES:
American Gastroenterological Association
http://www.gastro.org
National Institute of Diabetes and Digestive and Kidney Diseases
https://www.niddk.nih.gov
CANADIAN RESOURCES:
Canadian Association of Gastroenterology
https://www.cag-acg.org
Canadian Digestive Health Foundation
http://www.cdhf.ca
REFERENCES:
Hydrogen breath test for lactose intolerance. Cleveland Clinic website. Available at: https://my.clevelandclinic.org/health/diagnostics/12360-hydrogen-breath-test-for-lactose-intolerance. Accessed August 20, 2021.
Short bowel syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/short-bowel-syndrome. Accessed August 20, 2021.
Small intestinal bacterial overgrowth (SIBO). Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/gastrointestinal-disorders/malabsorption-syndromes/small-intestinal-bacterial-overgrowth-sibo. Accessed August 20, 2021.
Last reviewed July 2021 by
EBSCO Medical Review Board
James Cornell, MD
Last Updated: 8/20/2021