Health Encyclopedia

Small bowel bacterial overgrowth

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

Causes, incidence, and risk factors

Normally, the small intestine contains a relatively 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 many of the nutrients for their growth that a person should absorb. As a result, a person with the condition 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 lining the intestinal wall.

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

A problem with the immune system (immunodeficiency), such as AIDS or immunoglobulin deficiency
Complications of diseases or surgery that create pouches or blockages in the small bowel, such as Crohn's disease
Diseases that slow small bowel movement, such as diabetes and scleroderma
Short bowel syndrome caused by surgically removing a large part of the small intestine
Small bowel diverticulosis, in which small sacs of the inner lining of the intestine stick out, 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 intestinal bacteria can grow excessively

Symptoms

The most common symptoms are:

Abdominal pain and cramps
Bloating
Diarrhea (usually watery)
Fullness

Other symptoms may include:

Fatty, floating stool
Weight loss

Signs and tests

Low red blood cells (anemia) is a sign.

Treatment

The goal is to treat the cause of the excess 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.

Complications

Severe cases lead to malnutrition. Other possible complications include:

Dehydration
Excess bleeding due to vitamin deficiency
Liver disease
Osteoporosis

References

Prather C. Inflammatory and anatomic diseases of the intestine, peritoneum, mesentery, and omentum. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 145.

Review Date:10/13/2008
Reviewed By:David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and 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., Inc.

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