Small intestinal bacterial overgrowth: a comprehensive review

Abstract

Small intestinal bacterial overgrowth (SIBO), defined as excessive bacteria in the small intestine, remains a poorly understood disease. Initially thought to occur in only a small number of patients, it is now apparent that this disorder is more prevalent than previously thought. Patients with SIBO vary in presentation, from being only mildly symptomatic to suffering from chronic diarrhea, weight loss, and malabsorption. A number of diagnostic tests are currently available, although the optimal treatment regimen remains elusive. Recently there has been renewed interest in SIBO and its putative association with irritable bowel syndrome. In this comprehensive review, we will discuss the epidemiology, pathogenesis, clinical manifestations, diagnosis, and treatment of SIBO.

Keywords: Bacterial overgrowth; antibiotics; bloating; diarrhea; motility disorders; small intestinal bacterial overgrowth.

Figures

Figure 1

Billroth II anatomy that may predispose some patients to small intestinal bacterial overgrowth. Reproduced with permission from Lawrence PF, editor. Essentials of general surgery. Philadelphia[PA]: Lippincott Williams & Wilkins; 2005. p 262.

Figure 2

Roux-en-Y anastomosis that may predispose some patients to small intestinal bacterial overgrowth. Reproduced with permission from Lawrence PF, editor. Essentials of general surgery. Philadelphia[PA]: Lippincott Williams & Wilkins; 2005. p 265.

Figure 3

Lactulose breath test in a patient without evidence of small intestinal bacterial overgrowth.

Figure 4

Lactulose breath test in a patient with small intestinal bacterial overgrowth—note the elevated fasting hydrogen level and subsequent rise greater than 20 ppm.

Figure 5

Lactulose breath test with a double peak seen in some patients with small intestine bacterial overgrowth.