Small bowel bacterial overgrowth synrome (SBBOS), or small intestinal bacterial overgrowth (SIBO), also termed bacterial overgrowth; is a disorder of excessive bacterial growth in the small intestine. Unlike the colon (or large bowel), which is rich with bacteria, the small bowel usually has less than 104 organisms per millilitre. Patients with bacterial overgrowth typically develop symptoms including nausea, bloating, vomiting and diarrhea, which is caused by a number of mechanisms. The diagnosis of bacterial overgrowth is made by a number of techniques, with the gold standard diagnosis being an aspirate from the jejunum that grows in excess of 105bacteria per millilitre. Risk factors for the development of bacterial overgrowth include the use of medications including proton pump inhibitors, anatomical disturbances in the bowel, including fistulae, diverticula and blind loops created after surgery, and resection of the ileo-cecal valve. Small bowel bacterial overgrowth syndrome is treated with antibiotics, which may be given in a cyclic fashion to prevent tolerance to the antibiotics.