Diagnosis of small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) is a very rare cause of gastrointestinal symptoms. The symptoms overlap with irritable bowel syndrome (IBS), which leads to some patients with IBS being misdiagnosed as having SIBO. The diagnosis and prevalence of SIBO is controversial. No gold standard exists for the definition and diagnosis of SIBO.

The symptoms of SIBO can be confused with IBS. SIBO should be considered in patients diagnosed with IBS, particularly elderly patients whose predominant symptoms are bloating and flatulence.

In a small number of patients, SIBO can cause elevated serum folate, steatorrhea or vitamin B₁₂ deficiencyQuigley, 2020.

All patients suspected of having SIBO should be referred to a gastroenterologist for diagnosis and management.

Note: Refer all patients suspected of having SIBO to a gastroenterologist for diagnosis and management.

Hydrogen breath testing (using lactulose or glucose as the test substrate), carbon-14 D-xylose breath testing, or small bowel aspirate can be used to support the diagnosisQuigley, 2020. However, these tests have significant limitations, including poor sensitivity and specificity, and no consensus on their interpretation.