Small Intestinal Bacterial Overgrowth (cont.)

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What causes small intestinal bacterial overgrowth?

The gastrointestinal tract is a continuous muscular tube through which digesting food is transported on its way to the colon. The coordinated activity of the muscles of the stomach and small intestine propels the food from the stomach, through the small intestine, and into the colon. Even when there is no food in the small intestine, muscular activity sweeps through the small intestine from the stomach to the colon.

The muscular activity that sweeps through the small intestine is important for the digestion of food, but it also is important because it sweeps bacteria out of the small intestine and thereby limits the numbers of bacteria in the small intestine. Anything that interferes with the progression of normal muscular activity through the small intestine can result in SIBO. Simply stated, any condition that interferes with muscular activity in the small intestine allows the bacteria to stay longer and multiply in the small intestine. The lack of muscular activity also may allow bacteria to spread backwards from the colon and into the small intestine.

Many conditions are associated with SIBO. A few are common.

  • Neurologic and muscular diseases can alter the normal activity of the intestinal muscles. Diabetes mellitus damages the nerves that control the intestinal muscles. Scleroderma damages the intestinal muscles directly. In both cases, abnormal muscular activity in the small intestine allows SIBO to develop.
  • Partial or intermittent obstruction of the small intestine interferes with the transport of food and bacteria through the small intestine and can result in SIBO. Causes of obstruction leading to SIBO include adhesions (scarring) from previous surgery and Crohn's disease.
  • Diverticuli (out-pouchings) of the small intestine where bacteria can live and multiply and are not swept away by the intestinal activity. Diverticuli of the colon, an extremely common condition is not associated with SIBO.
Medically Reviewed by a Doctor on 3/10/2014

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