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Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) is common and effects up to 15% of the population in any given year. IBS appears to effect women more commonly than men and although it often presents in young people it my occur at any age.


Irritable bowel syndrome (IBS) is a chronic disorder characterised by abdominal pain and change in bowel habit as a consequence of abnormal visceral sensation and or motility,arising as a result of abnormalities within the enteric or central nervous systems,  or both. Usually this occurs in the absence of structural or inflammatory (“organic”) disease but association with other gastrointestinal disease is common. Disturbances in the gastro-intestinal microbiome have been identified in patients with irritable bowel syndrome and it is often the case that symptoms may be triggered by events which lead to changes in microbiome, emotional context and enteric nervous function in tandem


The diagnosis of IBS should be considered in any patient presenting with the combination of abdominal pain, altered bowel habit and or abdominal bloating. Patients may complain of constipation, diarrhoea or may fluctuate between the two. In order to meet the current diagnostic criteria patients should have had symptoms for at least six months, although clearly patients with identical symptom complexes for a shorter period are clearly likely to have similar pathology, whilst not strictly meeting the current diagnostic criteria. Many patients also complain of associated symptoms such as faecal urgency and incomplete evacuation. Extra gastrointestinal symptoms including fatigue and poor concentration.


In all patients with symptoms consistent with a diagnosis of IBS the presence of “red flags” or symptoms that may suggest another pathology should be specifically sought and excluded. Red flags include a new change in bowel habit lasting for more than 6 weeks in a person aged 60 years or older, the occurrence of rectal bleeding, unexplained weight loss and a history of ovarian or bowel cancer within the immediate family. If any red flags are present they should be explored and further details sought. An assessment should then be made and consideration given to whether a referral to a gastroenterologist should be undertaken.


In patients who are presenting for the first time a number of routine tests should be arranged including full blood count, to exclude anaemia, coeliac serology,  inflammatory markers and probably a faecal calprotectin. The reason for undertaking these investigations is to ensure that organic disease which requires specific investigation or therapy is not missed. Inflammatory bowel disease, occult neoplasia (cancer) and coeliac disease can all mimic many of the symptoms of IBS. However in the context of a suggestive history, in the absence of red flags, if these investigations have been normal they do not need to be repeated. Nor do patients with typical symptoms require further invasive endoscopic investigations.


Whilst healthcare professionals have an important role in excluding other disease and in providing education and empowerment for patients who are struggling with their symptoms, patients should be encouraged to take an active role in identifying their individual symptom triggers and in managing the dietary, lifestyle and psychological factors which may exacerbate their symptoms. The IBS Network is a national charity that supports patients with IBS and offers a range of services including information and a telephone helpline to which members have access. Patients may find it a useful resource from which they can obtain further support and information. Medicines are not usually the mainstay of effective management for patients with IBS, but rather should be used to target and alleviate specific symptoms.


Approximately 40% of patients will already recognise dietary triggers. For many a dietary review and basic advice and support may be sufficient to alleviate symptoms. Initial review should assess the frequency of meal and food intake and make sure that common precipitants are minimised. Patients should be encouraged to eat regularly and not leave long gaps between meals. Common dietary triggers include caffeine, fizzy drinks, which often cause bloating, alcoholic beverages and diet drinks, that often contain indigestible sugars that may ferment within the large bowel and cause bloating and erratic bowel habit. Foods containing resistant starches, commonly encountered in some pre-prepared and processed meals may also reach the large bowel where they may be fermented by colonic bacteria and cause similar symptoms. Simply reducing these foodstuffs where they form a large part of the diet may be sufficient to relieve symptoms. If diet remains a likely trigger then the expert support of an appropriately trained healthcare professional (such as a dietitian) should be sought to explore the possibility of exclusion diets. Common exclusion diets include those excluding wheat, dairy produce or FODMAPs (fermentable oligosaccharides, disaccharides monosaccharides and polyols).  Professional support from an appropriately trained individual is key, not necessarily because these things are hard to exclude, although a low FODMAP diet is very challenging to execute well, but because all exclusion diets should be continued for a limited period and therefore require the structured re-introduction of foods to ensure the diet is replete in the required nutrition whilst avoiding the provocation of symptoms. For those looking for NHS Webinars on diet here is a useful link ;


Diet is clearly important but other lifestyle factors also influence the genesis of symptoms in IBS. We cannot always influence the stresses that we face however a number of factors can exacerbate symptoms including poor sleep, lack of exercise and relaxation. These three factors are inextricably linked to each other and to the normal functioning of the gut. For patients who are sleeping poorly good sleep hygiene is important. Several online apps are available to support patients in this regard, similarly it is important for patients to find time to relax, the NICE guidance suggests we should all find twenty minutes to relax on a daily basis, and there are numerous apps available to try and facilitate this, some may simply prefer to embed themselves in a good book. Exercise is underrated as a therapy. Again the national guidance advises we take 150 minutes of exercise (that makes us slightly short of breath) every week. This often aids bowel habit, sleep and relaxation. Nevertheless some forms of exercise may provoke urgency, in which case it is best for patients to either be near an accessible toilet or to find forms of exercise that doesn’t provoke urgency. If patients are currently taking no regular exercise then they should start slowly and increase the length and frequency of exertion slowly, mindful of any co-morbidities.


Psychological intervention may also be of benefit and a range of psychological treatments have been shown to be effective. In general psychological interventions may be simple or for those with more complex psychological disease more complex(1). In general one in four to one in five patients will benefit from psychological intervention. This is a similar number needed to treat as for antidepressants.


A number of drugs are available to treat IBS. Whilst these are targeted at specific symptoms they broadly fall into three overlapping categories as follows, drugs which effect bowel sensitivity, such as peppermint oil, drugs which effect bowel motility and stool consistency. These can be subclassified into aperients, antidiarrheals such as loperamide and anti-spasmodics such as mebeverine, alverine or hyoscine butylbromide. In general lactulose should be avoided, since it is a FODMAP and tends to cause bloating and occasionally abdominal pain. Often PEG based laxatives such as movicol or laxido are a good starting point for patients with constipation. In such patients measured regular use combined with lifestyle change is a better approach than sporadic use of large doses which often leads to oscillation between loose and constipated stools. Lastly a number of drugs may effect the nervous processing of visceral sensation and can be used to modulate abdominal pain. These often have side-effects that alter bowel habit so this needs to be born in mind when they are prescribed. There is reasonable evidence for the use of tricyclics such as amitriptyline at a dose of 10mg at night (increasing to a maximum dose of 30mg), but patients need to be made are that such drugs may have significant side effects. Medication which has no clear benefit should be stopped.


Probiotics are not drugs however there is a growing body of evidence to support their use Their effects are likely to be strain specific so if after a months patients have seen no benefit it is sometimes worth trying an alternative. The commonest side effect is bloating. Gut directed hypnotherapy is a well established intervention with a good evidence base but unfortunately is only available in a limited number of areas.

Links between Periods, menopause and IBS

IBS is a long-term condition that is characterised by symptoms of abdominal pain altered bowel habit and frequently bloating in the absence of alternative diagnoses, such as inflammatory or neoplastic disease. It is often regarded as a disorder of the way the gut nervous system interacts with the intestinal organisms, the lining of the bowel and the central nervous system. A range of abnormalities of gut motility and sensitvity are well recognised as part of this condition. These abnormalities may be a result of abnormalities within the organisms within the bowel, the lining or the gut or central nervous system. Triggers for changes in sensitivity and motility in the gut and thence symptoms may include dietary components, gut inflammation or irritation (typically following infection) and changes in environment including social and psychological stress.

Irritable bowel syndrome appears to be commoner in women than men and many women between the age of puberty and menopause recognise that their symptoms are worse at particular times during their menstrual cycle. Most studies suggest symptoms are worst pre- and during menses. Women with irritable bowel syndrome often find that symptoms may improve once they have reached the menopause, though this is not universal. For all these reasons these observations have led to interest in whether and how gut symptoms are influenced by changes in sex hormones, particularly oestrogen and progesterone.

To date animal studies examining the effect of sex hormones on bowel motility and sensitvity have been inconclusive, with a range of different studies demonstrating different outcomes; perhaps all rats are not the same, just as with humans!

Studies in healthy human women have not to date drawn altogether consistent conclusions, on the whole it appears that sex hormones have only minor effects on gut motility and sensitvity in people who don’t already have gastrointestinal symptoms. Some studies suggest the gut motility appears to increase during the luteal phase of the cycle when oestrogen and progesterone levels are at their highest. However women with IBS appear to have rather different responses, perhaps reflecting pre-existing changes within the nerves and tissues within the gut that make them more susceptible to the effects of these hormones on the gut.

The effects hormones result in changes in motility, sensitvity at a local level within the gut (a bit like sensitvity in skin that looks normal but itches) or sensitvity driven by changes in the central nervous system, either within the gateways of the spinal cord or as a result of changes in the brain, which is influenced by external factors in the environment. There is good evidence that both oestrogen and progesterone can have effects on all these pathways.

Gut motility is influenced by oestrogen through its effect on receptors and ion channels within the muscle of the bowel wall. In general rising levels of oestrogen lead to increase in the motility of bowel muscles through the effect of the hormone on potassium and calcium channels. These ions are important factors in contractility of smooth muscle within the gut. Conversely progesterone appears to reduce gut contractility through its effect on a group of proteins known as G-proteins which act as a kind of molecular switch within the muscle cells.

Gut sensitivity can be influenced locally (at the level of the mucosa) or centrally (within the central nervous system). Sex hormones have significant influence on both this mechanisms. Oestrogen enhances the levels of serotonin, a key neurotransmitter in both the gut and the brain, by inhibiting serotonin re-uptake (similar to the anti-depressants known as SSRIs , which are sometimes used to treat IBS) and promoting serotonin synthesis. Paradoxically perhaps oestrogen may increase visceral sensitvity by enhancing the responsiveness of cortisol receptors in the enteric (gut) nervous system, during times of stress. Inflammatory cells known as lymphocytes, which help to co-ordinate immune regulation within damaged and healthy tissues have oestrogen receptors on their surface.  Both of the main types of lymphocytes (T and B Cells) are influenced by oestrogen, which appears to dampen their response to inflammatory stimuli, this may then attenuate local sensitvity. Progesterone also appears to have significant effects on nerves carrying messages from the gut to the central nervous system, these effects may vary depending on the quantity of progesterone. At the time of mensturation the uterus also produsces a host of messengers known as prostaglandins, which are key to the control of inflammation and pain. These uterine messengers may also have effects on muscular function and pain perception in other tissues including the gut. The precise effects of the sex hormones is likely to be dependant on not only the concentration of the particular hormone but also the effects of other molecules and environmental influences. This may explain why the precise influence of specific hormones is simple or less predictable than we might initially anticipate.

Nevertheless there is no doubt sex hormones have a significant influence on the symptoms patients experience. Some patients find modulating these with HRT or the contraceptive pill can benefit their symptoms, others may find the converse. Nevertheless this does not negate the importance of attending to those factors which we can influence, like diet, lifestyle (Sleep/stress/ relaxation and exercise) as well as the psychological factors which we know can precipitate symptoms.

An overview of the diagnosis and treatment of IBS

Making the Diagnosis

What causes IBS?

IBS - Brain-Gut Axis

IBS - Microbiome

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IBS Manegement

IBS - Manegement Overview

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IBS - Diet

IBS- Lifestyle

Clinical Manegement - Psychology

IBS- Prebiotics and Probiotics

IBS - Drugs

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