Diagnosing Small Intestinal Bacterial Overgrowth (SIBO)
Learn about the tests that can considered to assess and diagnose SIBO.
CONTACT USUnderstanding SIBO Diagnosis
SIBO can lead to many of the same symptoms as IBS. It has been found that the majority of those with IBS actually have SIBO as the root cause. While there is not a specific test for IBS, SIBO can be tested for and diagnosed via 2 main test.
The symptoms that may indicate SIBO is present and that testing may be needed include:
- Bloating, often soon after eating
- Abdominal pain
- Food reactions, often to high fibre foods
- Changes in bowel patterns (eg constipation or diarrhoea)
SIBO Tests for diagnosis
The tests for SIBO assess the levels of bacteria in the small intestine.
The 2 tests that are considered for SIBO diagnosis are:
Hydrogen and Methane SIBO Breath Test
Due to it’s non-vasive nature, this test is commonly used in clinical practice. It involves drinking a test solution of either lactulose or glucose, and collecting breath samples every 20 minutes for 3 hours. This provides an understanding of the bacterial fermentation taking place in the small intestine.
Small Intestine Aspirate and Culture
This SIBO test is more commonly used in hospital assessments and clinic research. It is a test for SIBO that involves collecting a small of the fluid from the small intestine. This is then assessed in a laboratory for the concentration of bacteria in the fluid.
SIBO Breath Testing for Hydrogen and Methane
SIBO breath tests involve the introduction of a fermentable sugar into the digestive system. This is either lactulose or glucose. Both of these sugars are easily fermentable by the bacteria in the digestive tract.
During the fermentation process, hydrogen and/or methane gases can be produced. These gases are absorbed into circulation from the gut and then to the lungs where they are exhaled.
During a SIBO breath test, the levels of hydrogen and methane gases are collected. The concentration of these gases is then assessed. If a certain levels of these gases are present SIBO is diagnosed.
Small Intestine Aspirate and Fluid Culture
Due to its more invasive and complicated nature, the small intestine aspirate and fluid culture test for SIBO is not used as regularly as the SIBO breath test. However, it is considered the gold standard test for SIBO.
The test is carried out in a hospital or clinical setting and a tube is inserted into the small intestine via the mouth. This tube can then collect a fluid sample from the small intestine.
This sample is assessed through a culturing process where the concentration of bacteria is reported. If a specific concentration is reached, SIBO is diagnosed.
Additional Tools for Diagnosing SIBO
SIBO breath tests and small intestine aspirate and fluid culture tests are the only 2 tests that can be used to diagnose SIBO. However, other tests may be considered to provide information about the health of the digestive tract and imbalances in the gut microbiome.
- Microbiome analysis
- Organic acids tests (OAT)
- Calprotectin stool test
Additionally, SIBO breath tests may provide false negative results. This means that practitioners may often treat SIBO empirically. This is where treatment for SIBO is started based on symptoms and health history.
Blood Tests for Vitamin Deficiencies
Due to a restricted diet or malabsorption of nutrients in the small intestine, those with SIBO may have vitamin and mineral deficiencies.
These can be assessed via blood tests and include deficiencies in:
- Vitamins A, D, E and K
- Iron
- B12
It’s possible to take supplements to restore levels of these nutrients. As well as this, periodic retesting is suggested to assess and monitor response.
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SIBO Stool Evaluation for Fat Malabsorption
A bacterial overgrowth in the small intestine is associated with malabsorption. This can be the malabsorption of sugars as well as fats. While fat malabsorption often results in an oily or pale-looking stool, the stool may also look normal or non-oily.
A stool test can assess for fat malabsorption which may then allow for a more targeted approach. This may be in the form of reducing dietary fats as well as providing support via the introduction of digestive enzymes.
How Do You Get Diagnosed with SIBO?
A SIBO diagnosis can only be officially made by a doctor or gastroenterologist. This diagnosis will be made following a glucose or lactulose breath test for SIBO that assesses for hydrogen and methane or following a small intestine aspirate and fluid culture test.
Following a diagnosis of SIBO, specific treatments are discussed which may involve
- Antibiotics
- Antimicrobial herbs
- Probiotics
- Prebiotics
- Prokinetics
Imaging Tests for Structural Abnormalities
Various imaging procedures are considered during the diagnostic process for digestive issues.
Commonly, these tests are carried out ahead of a SIBO test to identify any structural abnormalities in the bowel. In cases of SIBO, these abnormalities may result in the narrowing of certain sections of the bowel, leading to a bacterial overgrowth.
These tests include:
- X-rays
- CT scans
- MRI scan
Preparing for Your SIBO Tests
Prparation for a SIBO test can involve discontinuing certain medications and supplements and well as following a low fibre diet for the day before the test.
- Antibiotics – It is recommended that a SIBO test isn’t performed within 4 weeks of completing a course of antibiotics.
- Probiotics – It is recommended that probiotics supplements be paused for the 7 days leading up to a SIBO breath test.
The foods to eat for the 24 hours leading up to the SIBO test are:
- Chicken
- Fish
- Turkey
- Beef
- Lamb
- Pork & ham
- Eggs
- Tofu
- Black/green tea (not herbal)
- Coffee (without milk)
- Plain boiled white rice
- Tomato (no skins)
- Breads (white, low fibre)
- Jelly and jam – (no artificial sweeteners).
Understanding SIBO Test Results
The results of a hydrogen and methane SIBO breath tests are assessed using specific criteria. This takes into account the levels of hydrogen and methane and at which part of the test the levels increase.
Hydrogen Positive Criteria
An increase of at least 20ppm in Hydrogen above the baseline (first sample) within 90 minutes of the test.
Methane Positive Criteria
A levels of methane which is greater that 10ppm at any point during the test.
The specialist ordering the test will review the results and provide their interpretation of the findings. This will help to guide treatment options and further considerations.
Conclusion
SIBO tests can be an important step in the diagnostic process and allow for more efficient treatment. A specialist will be able to recommend the appropriate tests and based on the results, the appropriate treatment.
Alongside this, if SIBO is present, understanding and addressing the underlying cause of the bacterial overgrowth also needs to be considered.
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