Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine.

The bacterial overgrowth syndrome constitutes an intestinal problem involving alterations in motility and injury to the brush border and mucosa. The overgrowth of bacteria also causes secretion, malabsorption, and maldigestion. These alterations result in a clinical syndrome that manifests itself as weight loss, malabsorption of specific nutrients, and (usually) diarrhea. There are known causes of bacterial overgrowth, such as intestinal diverticuli or surgical procedures involving a vagotomy, but in our experience most cases remain idiopathic. This review evaluates the mechanisms of bacterial overgrowth, as currently understood, and specifically addresses the known causes of diarrhea that results from bacterial contamination of the small intestine.