Small Intestinal Bacterial Overgrowth

Abstract

Small intestinal bacterial overgrowth (SIBO) is defined as the presence of an abnormally high number of coliform bacteria in the small bowel. The predisposing conditions for the development of SIBO can be broadly grouped into disorders relating to hypochlorydia, enteric dysmotility, immune deficiency, and altered small bowel anatomy. More recently, some investigators have implicated SIBO as a common cause for irritable bowel syndrome, although this association is clouded with controversy and remains doubtful. The symptoms of SIBO are protean and relate to direct injury to the small intestinal epithelium, as well as intra-luminal bacterial catabolism of nutrients; as such, patients may experience abdominal pain/discomfort, diarrhea, steatorrhoea, bloating, weight loss, and nutrient imbalances. The three tests currently available in routine clinical practice to help make a diagnosis of SIBO are culture of small bowel aspirates, the glucose hydrogen breath test, and the lactulose hydrogen breath test. However, they all have inherent problems with regards to accuracy, meaning that they should be interpreted with caution and alongside clinical suspicion before a diagnosis of SIBO is made. The treatment of SIBO includes eradicating bacterial overgrowth, treating nutritional deficiencies, and (where possible) addressing the underlying cause.