Small intestinal bacterial overgrowth syndrome (SIBO) is in vogue. Are clinical symptoms useful for diagnosis?

Abstract

Introduction: Small intestinal bacterial overgrowth syndrome (SIBO) is an entity derived from changes in the composition and quantity of bacteria in the small intestine. When this excess proliferation is due to methanogenic microorganisms, it is defined as intestinal methanogenic overgrowth (IMO). The clinical presentation is usually abdominal pain and/or distension and diarrhoea, and its development is associated with different risk factors. Inhaled hydrogen tests are used for diagnosis. Despite being an increasingly frequent syndrome in recent years, scientific evidence is limited, and doubts arise in its management. The latest studies give considerable importance to the presence of risk factors, arguing that in patients without them the symptoms have a weak predictive value.

Objectives: To analyse the results of inhaled hydrogen lactulose tests performed in the children's gastroenterology office of the Hospital Universitario Donostia, describing the symptoms of those who were diagnosed with SIBO and those who were not, and investigating the presence of risk factors.

Methods: Retrospective descriptive study by reviewing medical records of patients who underwent lactulose test between June 2021 and October 2024.

Results: 67 tests performed, 57 analysed. The test was normal in 45%. SIBO 22.8%, IMO 17.54%, colonization of methanogenic microorganisms 14.03%. Sex distribution: 54.4% men and 45.6% women. Mean age at diagnosis: 9.45 years ± 2.62. The most frequent symptomatology was abdominal pain (91.22%), followed by flatulence (56.14%) and diarrhoea (50.88%). No relationship was found between clinical symptoms and diagnosis. Four patients presented risk factors, all of them in the SIBO group.

Conclusions: given the low correlation between symptoms and the presence of SIBO, and following the latest evidence, it would be advisable to consider the possibility of performing the test only in patients with clinical symptoms and compatible risk factors.