Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management

The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldiges-tion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.

Automated summary

The concept of small intestinal bacterial overgrowth (SIBO) explains the cause of maldigestion and malabsorption. With the development of diagnostic testing, the methods for diagnosing SIBO have evolved from small bowel culture to breath tests and culture-independent microbial analytics. The availability of breath tests has led to an expansion in the diagnosis of SIBO and the associated clinical symptoms. However, issues with the specificity of breath tests have raised doubts about the role of SIBO in certain clinical scenarios. The hope is to use modern molecular microbiology to study the human small intestinal microbiome in order to provide an objective basis for diagnosing SIBO.