What is Irritable Bowel Syndrome

Information Sheets

Irritable bowel syndrome (IBS) is an extremely common condition. Between 1.9 and 3.6 million patients consult a healthcare professional for IBS each year in the UK (1). The total population prevalence is much higher as most IBS sufferers are non-consulters due to the perceived lack of effective treatments.

IBS can be sub-classified based upon predominating bowel habit, i.e. constipation predominant (IBS-C), alternating bowel habit (IBS-A) or diarrhoea predominant (IBS-D) (2).

The main symptoms are abdominal pain / cramping, bloating, distension, nausea, flatulence, altered and/or unpredictable bowel habit, urgency to defecate which can lead to episodes of incontinence, fatigue, loss of appetite and anxiety.

Whilst IBS is not considered a life threatening condition it is a life altering condition which can affect sufferers severely in their day to day activities.

There may be many potential causes of IBS including changes in the location and composition of gut bacteria, increased bowel sensitivity, an inability to properly absorb bile acids in the small bowel, intolerances to foods, stress and previous psychological trauma. Identifying the most probable cause can help to target treatments which may include treating a combination of the above factors within the same patient.

For most people, IBS is a diagnosis of exclusion given when other conditions such as inflammatory bowel disease have been ruled out. The diagnosis is based on symptoms (as defined by the Rome III criteria) and the exclusion of ‘red flag’ symptoms such as rapid weight loss, bleeding from the rectum etc. Until recently, there has not been an objective test which provides a positive discriminatory diagnosis of IBS.

Once you have been given a diagnosis of IBS there is unfortunately little consensus on what further diagnostic testing could be needed, what treatment strategies should be employed and what positive treatment outcomes should look like to the patient and physician.

This can lead to frustration for IBS patients who are given a ‘functional’ diagnosis which is supposed to give reassurance but still leaves many questions to be answered. At the Functional Gut Clinic we work closely with your Doctor to form a ‘joined up pathway’ to make sure you diagnosis and treatment is optimized.

Recent work has shown that the composition and location of gut bacteria can cause symptoms which are experienced by IBS patients. For example, if you have bacteria in the small bowel (SIBO – small intestinal bacterial overgrowth), they will begin to ferment foods before your body has had chance to digest and absorb the nutrients.

This produces gas and acids (short chain fatty acids) within the small bowel which can lead to changes in sensitivity and motility. As the small bowel is not designed to cope with this fermentation it can lead to symptoms of nausea, bloating, pain, indigestion, heartburn, belching, fatigue and headache. As similar effects will be felt almost regardless of whatever foods you eat (healthy or not!) this can be very confusing for patients.

If the problem is with the composition of gut bacteria within the colon, this means that normal fermentation can become excessive or produce undesirable by-products which effect factors such as gut motility and sensation as well as make you feel generally unwell. It has recently been conceived that suffering from a previous gastrointestinal infection can change the gut microbiota and make people more susceptible to SIBO.

In recent years, several effective treatment approaches have been applied to IBS including dietary interventions (low fibre and low fermentable oligosaccharides, disaccha­rides, monosaccharides and polyols (FODMAP)), probiotics (VSL#3, Symprove etc) and pharmacological agents (linaclotide, Rifaxamin etc) (3).

Whilst each of these treatment approaches have shown efficacy, it is clear that further refinement of the IBS diagnostic algorithm is required to better target therapies in order to overcome the inherent heterogeneity (overlap of causes) within the IBS population which is how our tests help.

We perform a wide range of validated physiology tests at the Functional Gut Clinic which can tell us about how your gut is functioning and how that might be contributing to your symptoms.

These can include a full range of hydrogen and methane breath testing to see how bacteria and absorption of different carbohydrates may be contributing to your symptoms. We see this test as a provocation test which marries together physiological information about your gut with the symptoms you feel during the test to fully understand the clinical relevance of our observations. This helps you and your Doctor to devise a targeted plan to treat the different factors that might be contributing to your symptoms.

To find out more please view our Hydrogen and Methane Breath Testing information page.

We work closely with your Doctor to make sure everyone fully understands the implications of your test results. In some cases you may be referred on to our dietetics or bowel re-training specialists for none pharmacological treatment. We sometimes repeat tests to make see if your treatment has been effective.


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+44 (0) 207 486 7777


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M2 4NG

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