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Overview of diagnosis and management of Small Intestinal Bacterial Overgrowth

SIBO (small intestinal bacterial overgrowth) is a relapsing and remitting condition that affects up to one in seven people in the general population. The hallmark of SIBO is that the small intestine becomes colonised with bacteria. These can cause a variety of symptoms, including:

  • Bloating
  • Abdominal discomfort
  • Gas (flatulence)
  • Diarrhoea
  • Fatigue

For many years patients with SIBO symptoms have been misdiagnosed with irritable bowel syndrome. This is primarily because there is a lack of consensus regarding the diagnostic criteria for the disease. There is also a lack of robust data on the ideal treatment for SIBO.

The small intestine does not normally have any bacterial colonisation. However, in SIBO, bacteria that normally live in the large bowel start to grow within the small bowel. These bacteria feed off the sugars in the foods that people eat thereby causing flatulence and problems with digestion or absorption of food.

Several risk factors have been identified for SIBO although it can occur in healthy individuals too. Risk factors include:

  • Previous small bowel resection
  • Gastric bypass
  • Drugs such as narcotic pain killers, anti-diarrhoeal agents
  • Proton pump inhibitors
  • Connective tissue disorders such as fibromyalgia, Ehlers-Danlos syndrome and rheumatoid arthritis who are predisposed to relapsing symptoms of small intestinal bacterial overgrowth.

Testing for SIBO

Although there is no universally-accepted gold-standard test for SIBO, a commonly used diagnostic tests is the lactulose breath test. Before the test begins patients breathe into a balloon to allow the baseline measurement of the concentration of hydrogen in a normal breath. The patient then consumes a small amount of lactulose and the quantity of hydrogen and methane in exhaled breath is then measured by asking the patient to breath into a balloon every 15 minutes, for up to 3 hours. The amount of gas and the way it changes during the test is an indicator of the number of bacteria within the gut. Normal gas production in the small intestine in the first 120 minutes of the breath test should be less than 20ppm (parts per million) of hydrogen and less than 12ppm of methane.

Treating SIBO

Treatment of SIBO in comprises three strategies:

  • Inducing remission of SIBO
  • Preventing SIBO relapse
  • Treat or modify the underlying cause or predisposing factors

Inducing remission of SIBO

  • This primarily involves a course of antibiotics such as Rifaximin (although, despite its apparent effectiveness, it is not licensed by NICE and so is unavailable on the NHS in most hospitals and GP practices).
  • A second antibiotic such as Neomycin may also be used
  • Prucalopride (which increases gut motility) may be used as an adjunct therapy to antibiotics.
  • Herbal therapies are also sometimes used
  • It is unclear how helpful probiotics are in the treatment of SIBO. Probiotics can make symptoms slightly worse in the short term.

Preventing SIBO relapse

  • Diet – Limiting fermentable carbohydrates and following a diet such as the low FODMAP diet
  • Prokinetics such as Resolor (prucalopride) can help in optimising gut motility and preventing SIBO relapse
  • Herbal therapies such as iberogast
  • Digestive and pancreatic enzymes therapies may also be used
  • If the above methods fail, an elemental diet may be tried
    - This is a diet that consists of a liquid formula of pre-digested carbohydrates, proteins and fats.
    - As a result the nutrients are absorbed more quickly and can help prevent bacterial overgrowth by quickly eliminating the “fuel” bacteria need to replicate.
    - This is normally done under the supervision of a dietician.
    - Patients may stay on the liquid diet for up to 3 weeks.

Treating underlying causes

Since SIBO can occur in healthy people, it is not always possible to identify an underlying cause. This is something that needs to be discussed with a doctor. Various tests can be undertaken to look for causes and this needs to be considered on a patient-by-patient basis.

If you would like to make an appointment to be tested for SIBO or discuss management of your SIBO then please contact Dr Rehan Haidry at The London Gastroenterology Centre.

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Overview of diagnosis and management of Small Intestinal Bacterial Overgrowth

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