Small bowel bacterial overgrowth is a syndrome that involves very large numbers of bacteria growing in the small intestines.

The abnormally large numbers of bacteria in the small intestine compete for nutrients with the person who has the condition. As a result, the person with the condition may not absorb enough nutrients.

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

Intestinal bacteria overgrowth can be seen with many different disorders, including:

• Surgical procedures -- for example, a Billroth II type of gastrectomy can block the duodenum and jejunum, causing intestinal bacterial overgrowth
• Short bowel syndrome
• Diseases that slow small bowel movement, such as diabetes and scleroderma
• Small bowel diverticulosis -- small protruding sacs of the inner lining of the intestine; although these sacs can happen anywhere along the intestinal tract, they are more common in the large bowel than the small bowel.
• Complications of diseases or surgery that create blind pouches or obstructions in the small bowel, such as Crohn's disease, Billroth II gastrectomy, and small bowel diverticulosis
• Diseases such as chronic pancreatitis, cirrhosis of the liver, alcoholism, and end-stage renal disease
• Immunodeficiency, such as AIDS

The most common symptoms are abdominal pain and cramps, fullness, bloating, and diarrhea. The diarrhea can be watery or bloody. Other symptoms may include:

• Anemia (low levels of red blood cells)
• Weight loss
• Fatty, floating stool