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Small Intestinal Bacterial 

is the presence of excessive numbers of bacteria in the small bowel, causing gastrointestinal symptoms including bloating, abdominal pain, cramps, diarrhoea, constipation, excess gas

Cause of Small Intestinal Bacterial Overgrowth (SIBO) can be varied and multifactorial. It often involves disruption of normal mechanisms, that normally maintain small bowel homeostasis (prevent SIBO). Conditions associated with SIBO include: 

  • Mechanical e.g. post surgical, volvulus.

  • Motility e.g. IBS, pseudo-obstruction, visceral myopathies, mitochondrial diseases.

  • Medications e.g. Opiates, anti-secretory agents.

  • Malabsorptive conditions e.g pancreatic insufficiency, cirrhosis due to altered bile acid composition.

  • Systemic e.g. diabetes, scleroderma, amyloidosis.

  • Immune-related e.g. IgA deficiency.

  • Other e.g. ageing, small bowel diverticulosis.

SIBO Pathophysiology 


A breath test is most commonly used for diagnosing SIBO. Small bowel aspirate (gold standard method) however is less commonly used as it's invasive.

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Management of SIBO

  • SIBO is treated with antibiotics (e.g rifaximin) broad spectrum and minimal absorbed.

  • Prokintetics (used in case of gastroparesis to increase motility) 

  • Cause of SIBO needs to be determined to best prevent recurrence.

  • Diet modification plays a role in the management of this conditions.

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The Low FODMAP Diet for SIBO 

The low FODMAP diet has been recently evaluated as a potential treatment tool for SIBO, as it limits intake of highly fermentable carbohydrates and thus reduces the "food" available for the excess bacteria in the small bowel, "starving them out. FODMAP is an acronym for Fermentable Oligo-, Di, Mono-saccharides And Polyols. It is considered to be a second-line dietary strategy after assessment and management of dietary and lifestyle factors that may contribute to symptoms. 

The low FODMAP diet involves collective restriction of a group of short-chain carbohydrates that have been shown to  increase small intestinal water volume and be rapidly fermented in the large intestine, leading to increased gas (e.g. hydrogen) production and gastrointestinal symptoms (i.e. pain, bloating, distension, flatulence, nausea and altered bowel motility).

The low FODMAPs diet is a dietitian-taught program to ensure nutritional intake adequacy despite food restrictions. The long-term restriction of FODMAPs is not recommended. Structured reintroduction of  FODMAPs is recommended after two to six weeks to identify which FODMAPs you are sensitive to, your level of tolerance to each individual high FODMAP foods, and optimise food variety and self-management long term.


For individualised advice, book in now at the Dietetic Gut Clinic 

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