Unlike the large intestine, the small intestine does not have a high number of bacteria. When there are too many bacteria in the small intestine, these organisms use up the nutrients that would otherwise be absorbed into the body. A person with small bowel bacterial overgrowth may become malnourished as a result.
The breakdown of nutrients in the small intestine by the excess bacteria can also damage the intestinal lining. 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's disease is one of these conditions.
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 can occur anywhere along the intestinal tract, but they 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).
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).
Severe cases lead to malnutrition. Other possible complications include:
Semrad CE. Approach to the patient with diarrhea and malabsorption. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 142.
Jenifer K. Lehrer, MD, Department of Gastroenterology, Frankford-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.