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Small bowel bacterial overgrowth

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

Causes

Normally, the small intestine contains a low number of bacteria. This is different from the large intestine, which contains large numbers of bacteria.

The abnormally large numbers of bacteria in the small intestine use for their growth many of the nutrients that a person would normally absorb. As a result, a person with small bowel bacterial overgrowth may not absorb enough nutrients and will be malnourished. In addition, the breakdown of nutrients by the bacteria in the small intestines can damage the cells that line the intestinal wall. This can make it even harder for your body to absorb nutrients.

In addition, the breakdown of nutrients by the bacteria in the small intestines can damage the cells lining the intestinal wall.

Too much growth of bacteria in the small intestine can occur with many different conditions, including:

  • Complications of diseases or surgery that create pouches or blockages in the small bowel, such as Crohn's disease
  • Diseases that lead to movement problems in the small bowel, such as diabetes and scleroderma
  • Immunodeficiency such as AIDS or immunoglobulin deficiency
  • Short bowel syndrome caused by surgically removing a large part of the small intestine
  • Small bowel diverticulosis, in which small sacs occur in the inner lining of the intestine, allowing too much growth of bacteria. Although these sacs can occur anywhere along the intestinal tract, they are much more common in the large bowel than in the small bowel.
  • Surgical procedures, such as a Billroth II type of stomach removal (gastrectomy) that creates a loop of small intestine where excessive intestinal bacteria can grow.

Symptoms

The most common symptoms are:

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

Other symptoms may include:

  • Fatty stool
  • Weight loss

Exams and Tests

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

Treatment

The goal is to treat the cause of the excess small intestinal bacteria growth. For certain conditions, antibiotics or drugs that speed intestinal movement (motility-speeding drugs) may be considered.

Treatment also involves getting enough fluids and nutrition.

Someone who is dehydrated may need intravenous (IV) fluids in a hospital. If the person is already malnourished, a type of nutrition given through a vein (total parenteral nutrition -- TPN) may be necessary.

Possible Complications

Severe cases lead to malnutrition. Other possible complications include:

Alternative Names

Overgrowth - intestinal bacteria; Bacterial overgrowth - intestine

References

Semrad CE. Approach to the patient with diarrhea andmalabsorption. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed.Philadelphia, PA: Saunders Elsevier; 2011:chap 142.

Update Date: 5/1/2012

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

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