Small bowel bacterial overgrowth

Toggle: English / Spanish

Definition

Small bowel bacterial overgrowth is a condition in which very large numbers of bacteria grow in the small intestine.

Alternative Names

Overgrowth - intestinal bacteria; Bacterial overgrowth - intestine; Small intestinal bacterial overgrowth; SIBO

Causes

Most of the time, the small intestine does not have a high number of bacteria. Excess bacteria in the small intestine may use up the nutrients needed by the body. As a result, a person may become malnourished.

The breakdown of nutrients by the excess bacteria can also damage the lining of the small intestine. This can make it even harder for the body to absorb nutrients.

Conditions that can lead to overgrowth of bacteria in the small intestine include:

  • Complications of diseases or surgery that create pouches or blockages in the small intestine. Crohn disease is one of these conditions.
  • Diseases that lead to movement problems in the small bowel, such as and .
  • Immunodeficiency such as AIDS or immunoglobulin deficiency.
  • Short bowel syndrome caused by surgical removal of the small intestine.
  • Small bowel diverticulosis, in which small sacs occur in the inner lining of the intestine. These sacs allow too many bacteria to grow. These sacs are much more common in the large bowel.
  • Surgical procedures that create a loop of small intestine where excess bacteria can grow. An example is a Billroth II type of stomach removal (gastrectomy).
  • Some cases of irritable bowel syndrome (IBS).

Symptoms

The most common symptoms are:

  • Abdominal fullness
  • Abdominal pain and cramps
  • Bloating
  • Diarrhea (usually watery)
  • Gassiness

Other symptoms may include:

  • Fatty stool
  • Weight loss

Exams and Tests

Your health care provider will perform a physical exam and ask about your medical history. Tests may include:

  • Blood chemistry tests (such as albumin level)
  • Complete blood count (CBC)
  • Fecal fat test
  • Small intestine x-ray
  • Vitamin levels in the blood
  • Small intestine biopsy or culture
  • Special breath tests

Treatment

The goal is to treat the cause of the bacterial overgrowth. Treatment most often consists of antibiotics. In some cases, drugs that speed intestinal movement (motility-speeding drugs) may be used. A low carbohydrate diet can be helpful.

Treatment also involves getting enough fluids and nutrition. A person who is dehydrated may need intravenous (IV) fluids in a hospital. A person who is malnourished may also need nutrition given through a vein (total parenteral nutrition -- TPN).

Possible Complications

Severe cases lead to malnutrition. Other possible complications include:

References

Manolakis CS, Rutland TJ, Di Palma JA. Small intestinal bacterial overgrowth. In: McNalley PR, ed. GI/Liver Secrets Plus. 5th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 44.

Quigley EMM. Small intestinal bacterial overgrowth. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 105.

Version Info

  • Last reviewed on 5/11/2016
  • Subodh K. Lal, MD, gastroenterologist with Gastrointestinal Specialists of Georgia, Austell, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch)

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2013 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.