Recently GastroLife hosted a webinar tilted: SIBO and IBS: How HMBT can aid in investigation and diagnosis. Below, we have outlined a summary from this webinar event.
The length of the average GI tract is about 30 feet in length. This is equivalent to 5 average sized men standing, or 2 giraffes, or a 3-storey residential building. Digestion begins in the mouth. Food is chewed, mixed with salivary juices, and passes down the oesophagus ‘food pipe’. It then enters the stomach where food is then broken down into smaller particles with the aid of gastric secretions.
After this, the particles pass into the small intestine, and this is where most of the absorption takes place. These products of digestion can then be absorbed, so your body can use them for energy, and cell growth and repair.
Lastly, any remaining content enters the colon, here is it broken down further by all the good bacteria we have in our large intestine. Finally waste products are eliminated.
Even with this brief overview, we can tell that the gut is a very complicated system and that’s why patients may be referred for different tests to investigate different parts of the digestive system.
Gut bacteria help regulate our immune system’s responses – It is estimated that our gut contains between 39 trillion bacterial cells and 100 trillion bacterial cells. About 70% of our immune system is located in our Gut.
Intestinal microorganisms provide an important role in metabolic and protective functions for the host. In terms of protective function, the microbes assist in preventing pathogens potentially invading the intestinal mucosa by inhibiting attachment and subsequent entry of such pathogens into epithelial cells. Important metabolic functions include the fermentation of nondigestible carbohydrates such as starches, cellulose and pectin’s
What is meant by the gut-brain axis?
We then discussed what is meant by our second brain and how our gut and brain interact with each other, how signals sent from our gut to our brain can affect our mood, and the connection to digestive symptoms. You can read more about the gut-brain axis here.
Remember, It is important not to self-diagnose as a number of conditions can cause similar symptoms to IBS but will have a different treatment. For this reason, it is important to arrange to see your GP/Family Doctor to arrange some baseline investigations.
Small Intestinal Bacterial Overgrowth
Small Intestinal Bacterial Overgrowth (SIBO) occurs when there is a higher-than-normal number of bacteria in the small intestine causing gastrointestinal symptoms.
Most of our gut bacteria reside in the large intestine and performs a variety of important roles in the body. A much lower number of bacteria are located in the small intestine. If there is an abnormally high number of bacteria in the small intestine, it can interfere with digestion and absorption.
Endoscopic findings are usually normal in patients with SIBO, however in severe cases inflammation may be seen. Similarly, abnormal laboratory findings are usually only seen in patients with complex or severe SIBO, such as B12 deficiency.
Consequences of SIBO include Inflammatory epithelial changes that may result in the dampening of villi, damage to the brush border, and altered cytokines/mediators which affects the absorption process.
The Breakdown and malabsorption of fats is another consequence of SIBO. This occurs because of bile acid deconjugation by intraluminal bacteria. In turn, this affects micelle formation. A significant concentration of conjugated bile acid is required for the formation of these micelles which transport the fat molecules across the intestinal lumen. Therefore, SIBO indirectly damages the absorptive mucosa and can lead to chronic diarrhoea which is secondary to poor fat digestion and absorption.
Anaerobic bacterial utilisation of Vitamin B12 within the intestinal lumen may result in a deficiency. In severe cases, Vitamin D and iron deficiencies can occur.
Most importantly, SIBO can very often affect the patient symptomatically. This can be both quite uncomfortable for the patient and can affect their lifestyle and/or quality of life. Symptoms are produced as a result of byproducts released by the bacteria when they compete with the natural digestive process and metabolise, particularly carbohydrates, within the lumen of the small intestine. Gasses such as hydrogen, methane and carbon dioxide and short-chain fatty acids are produced. These gasses can move in both an antegrade and retrograde direction through the GI tract and cause non-specific GI symptoms such as nausea, abdominal/epigastric discomfort, flatulence, abdominal distension. A large amount of CO2 remains in the small intestine and leads to bloating. Diarrhoea can also result from the short-chain fatty acid by-products. This is because they exert an osmotic effect and absorb water into the intestinal lumen. Methane gas slows down gut transit and may cause constipation.
Relationship between SIBO and IBS
Although they are two distinct gastrointestinal conditions that can often be interconnected. Many individuals diagnosed with IBS also have SIBO, and vice versa. Both SIBO and IBS can present with similar symptoms. This overlap in symptoms can sometimes make it challenging to distinguish between the two conditions without specific diagnostic testing. The exact cause of IBS is not fully understood, but it’s believed to involve various factors including changes in gut motility, visceral hypersensitivity, and alterations in the gut microbiome. SIBO, can also occur due to altered or impaired motility.
Testing
Hydrogen breath testing was developed because of the relative inaccessibility of the small intestine.
Hydrogen Methane Breath Testing (HMBT) is a technique that is directly and instantaneously capable of detecting small intestinal bacterial overgrowth (SIBO) and dietary malabsorption.
The ‘Gold Standard’ diagnosis of SIBO is through the culturing of jejunal aspirate. This however, has limitations since the intestinal bacterial flora may be present in the more distal segment of the small intestine. In addition to this, it is a costly and invasive method, many bacterial species do not grow in routine culture media, contamination of the endoscope can occur as it passes through the GI tract, contamination of the sample by oral and pharyngeal bacteria, and proper handling of the sample is required.
At Home testing options have been available for some time, but as a result of Covid-19 and infection control risks, home testing options were more widely optimised to ensure patients did not suffer considerable delays with hospital waiting times and that they felt safer performing the test at home – outside a hospital or primary health centre setting.
AGIP Council Guidance in Relation to GI Physiology Provision during the COVID-19 Pandemic: ‘home testing kits available for Hydrogen methane breath test procedures which would allow patients to carry out the test at home rather than coming into the hospital environment’
Other benefits associated with preforming the test at home include convivence – those that live far from the clinic, find it hard to get time off work, childcare issue, or if they suffer from severe symptoms may be more comfortable at home. Patient can also perform test at a time that suits them once the pre-procedure guideline has been followed.
If the patients opt for the home testing option, they are provided with a testing kit containing all the required consumables, an easy-to-follow testing instructions booklet, and the option of watching a video to help with the sampling technique and sample collection.
Breath samples are then sent back to GastroLife for analysis and a report is issued.
Based on different guidelines, such as the European guidelines and North American Consensus, some testing clinics will consider a positive SIBO result if there is an early rise in hydrogen of >10ppm above baseline within 60 minutes, or a rise of >20ppm over baseline within 90 minutes – depending on testing substrate used.
The North American Consensus recommends that a methane level ≥10ppm at any point during the study is diagnostic of methanogen overgrowth.
More information on the SIBO test can be found here.
