The Spectrum of Small Intestinal Bacterial Overgrowth (SIBO)

To critically review recent (past 3 years) literature on the definition, diagnosis, and management of small intestinal bacterial overgrowth (SIBO).

While various series continue to illustrate the occurrence of SIBO in disease states where well-known risk factors for its occurrence are present (hypochlorhydria, disorders of intestinal structure or motor function, pancreatic insufficiency, and chronic liver disease, for example), the current challenge is in defining the limits of SIBO. Is SIBO truly common among those with “functional” gastrointestinal symptoms where there is no evidence of maldigestion or malabsorption; the original hallmarks of SIBO? Our attempts to address this question continue to be hampered by the limitations of our diagnostic tool kit. There is hope—the application of modern molecular techniques to the study of the small intestinal microbiome, together with some innovative sampling techniques, such as real-time intestinal gas sampling, may soon allow us to truly define the spectrum of SIBO.

SIBO, once removed from its original confines as a cause of malabsorption syndrome, has proven to be an elusive and moving target. Only the most rigorous studies employing validated methodologies will finally corral this mysterious entity.