Irritable bowel syndrome is a chronic functional gastrointestinal disorder that presents with abdominal pain, related to defecation, accompanied by a change in stool frequency or form. Despite its impact on a patient’s quality of life, it has no effect on mortality.
A positive clinical diagnosis should be made if the characteristic symptoms are present and red flags are absent. Red flags should prompt specialist referral.
Consultations should be provided in an empathetic manner, addressing the concerns of the patient while providing reassurance.
Manipulating diet, with the assistance of a dietitian, is an appropriate initial treatment for irritable bowel syndrome. A low-FODMAP diet is an effective therapy.
Low-dose antidepressants improve symptoms but can be accompanied by adverse effects. Antispasmodic drugs have a limited role.
Psychological therapies and gut-focused hypnotherapy are effective if patients are willing to try them.
Irritable bowel syndrome is a functional gastrointestinal disorder meaning there are no biochemical or structural abnormalities on investigation.1 However, it is treatable and it is among the most common complaints presenting to GPs2 affecting about 9% of Australians.3
The syndrome is characterised by recurrent abdominal pain, related to defecation, and is associated with a change in stool frequency or form.4 It is subtyped by the predominant stool form as follows:
- diarrhoea predominant (IBS-D)
- constipation predominant (IBS-C)
- mixed subtype (IBS-M).
Box 1 - The Rome IV diagnostic criteria* for irritable bowel syndrome
Recurrent abdominal pain, on average, at least one day per week in the last three months associated with two or more of the following criteria:
- Related to defecation
- Associated with a change in the frequency of stool
- Associated with a change in the form (appearance) of stool
* Criteria fulfilled for the last three months with symptom onset at least six months before diagnosis.
Source: reference 5
Given the broad definition of irritable bowel syndrome, it is likely to represent multiple different conditions, each developing from unique pathophysiological mechanisms.6 These include intolerance to particular foods, hypersensitivity to pain and psychosomatic manifestations of anxiety or stress. Other associated mechanisms include low-grade inflammation, altered microbiota, genetic factors and altered 5-HT (5-hydroxytryptamine) metabolism.
Irritable bowel syndrome can result in significant disability, reduced quality of life and impaired workforce productivity.7 Fortunately, it is not directly associated with mortality8 or an increased risk of gastrointestinal malignancies.9
Irritable bowel syndrome is not a diagnosis of exclusion. A positive diagnosis should be based on the presence of characteristic symptoms4 (Box 1), and the absence of red flags. Patients with red flags should be referred for further investigation, including imaging or specialist review (Box 2).6 A significant proportion of patients with irritable bowel syndrome may have symptoms that overlap with another functional gut disorder.
Box 2 - Red flags that require further testing or specialist assessment
Age over 50 years, no previous colon cancer screening and presence of symptoms
Recent change in bowel habit in people over 50 years of age
Evidence of overt gastrointestinal bleeding (i.e. melaena or haematochezia)
Nocturnal pain or passage of stools
Unintentional weight loss
Family history of colorectal cancer or inflammatory bowel disease
Palpable abdominal mass or lymphadenopathy
Evidence of iron deficiency anaemia on blood testing
Positive test for faecal occult blood
Adapted from reference 6
Initial testing should be minimally invasive. Full blood counts, urea and electrolytes, C-reactive protein and liver function tests would constitute reasonable initial investigations.
Coeliac serology should be considered as there is a significantly increased risk of coeliac disease among patients with symptoms that fit the Rome criteria for irritable bowel syndrome.10 Genetic testing for coeliac disease is not recommended – it is unlikely to discriminate between irritable bowel syndrome and coeliac disease because more than 30% of the population share the HLA-DQ2/8 gene.11
The symptoms of irritable bowel syndrome share similarities with inflammatory bowel disease and gastrointestinal malignancies. The concern of organic gastrointestinal pathology, even in the absence of red flags, may prompt many clinicians to recommend an endoscopic assessment. There is no role for a faecal occult blood test to exclude gastrointestinal malignancy in patients with symptoms of irritable bowel syndrome.12 A normal faecal calprotectin test result, which measures intestinal inflammation, reduces the need for endoscopy to rule out inflammatory bowel disease.13
Understandably, many clinicians are not confident to make a diagnosis of irritable bowel syndrome without specialist assessment. However, clinicians should be reassured that patients presenting with symptoms of irritable bowel syndrome in the absence of red flags are extremely unlikely to be affected by serious organic illness.14
The treatment for irritable bowel syndrome should involve addressing the patient’s concerns, and prescribing treatments that tackle the mechanisms underpinning their symptoms.
An appropriately conducted consultation can be therapeutic for a patient with irritable bowel syndrome. However, only a minority of patients consult their GP, and an even smaller proportion seek specialist care.15
Clinicians should therefore recognise that patients who present with irritable bowel syndrome require a holistic consultation. A positive diagnosis and reassuring explanation of irritable bowel syndrome should be delivered in an empathetic manner, while allowing time for the patient to discuss their concerns. A randomised controlled trial showed patients who were given sham acupuncture were less likely to have adequate relief of irritable bowel syndrome symptoms compared with patients who received sham acupuncture combined with a ‘warm empathetic’ consultation (44% vs 62%, p<0.001).2
Many patients with irritable bowel syndrome report aggravated gastrointestinal symptoms related to specific foods.16 This perception lends itself well to a therapeutic manipulation of diet. However, clinicians should be mindful of overly restrictive eating patterns,17 and dietary manipulation should be supervised by a dietitian.
General dietary advice
The UK’s National Institute of Health and Care Excellence (NICE) recommends eating smaller frequent meals, avoiding trigger foods, and avoiding excess alcohol and caffeine. This diet has been found to be as effective as a low-FODMAP diet (low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols) for the diarrhoea-predominant irritable bowel syndrome.16
Insoluble fibres are more likely to worsen abdominal pain and bloating in patients with irritable bowel syndrome.6 However, soluble fibres such as psyllium improve symptoms, especially in patients with the constipation subtype.18
Foods containing FODMAPs (which are short-chained carbohydrates) are poorly absorbed by the small intestine. This leads to an osmotic effect in the colon and excess gas production causing pain and diarrhoea. A low-FODMAP diet has been proven to significantly reduce symptoms related to irritable bowel syndrome compared to a regular Australian diet.19 Patients with irritable bowel syndrome, especially those with the diarrhoea subtype, should consider a low-FODMAP diet as their initial therapy. Individual symptoms of pain and bloating seem to respond to this diet.
A dietitian-supervised low-FODMAP diet involves an exclusion phase where patients reduce FODMAP-containing foods over six weeks. If the patient reports a significant reduction in symptoms, FODMAP-containing foods can be carefully re-introduced over subsequent weeks. Remaining on an exclusively low-FODMAP diet in the long term has been shown to transform the intestinal microbiota to a potentially negative profile,19 and therefore is not recommended.
General lifestyle advice
Symptoms of irritable bowel syndrome can be mitigated by regular exercise20 which should be recommended in conjunction with dietary advice. The importance of sleep should also be discussed as improved quality of sleep has been found to control symptoms.21
Drugs exclusively developed for irritable bowel syndrome are not available in Australia, unlike the USA and Europe. Most of the drugs used here were designed for other indications.
Mebeverine and hyoscine
Antispasmodic drugs have only modest effects in irritable bowel syndrome and have a limited role.22 Although hyoscine has greater evidence for symptom relief,23 it is associated with significant adverse effects including constipation and dry mouth.
Antidepressants can significantly reduce symptoms of irritable bowel syndrome.26 They are purported to work by manipulating visceral hypersensitivity and abnormal central pain sensitisation.24 Tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs) have both demonstrated benefit.26 Tricyclics are ostensibly used for the diarrhoea subtype due to their known adverse effect of constipation. Similarly, SSRIs may be better used for the constipation subtype due to their adverse effect of diarrhoea. Although SSRIs have been shown to be of benefit,26 the exact dose and their use are not universally accepted for the treatment of irritable bowel syndrome.
It is important to advise patients that antidepressants are used for their neuropathic-pain-modulating effect, rather than for an antidepressant effect. Patients should take a low dose of the antidepressant every day for 4–6 weeks before assessing efficacy.
Rifaximin has a limited role in irritable bowel syndrome and it is not subsidised by the Pharmaceutical Benefits Scheme for this indication. It is a non-absorbed antibiotic that modestly reduces symptoms of non-constipating irritable bowel syndrome compared to placebo.27 Despite theoretical concerns of developing persistent bacteria that are resistant to rifaximin, studies have not demonstrated this to be the case.
Probiotics possibly have a role in irritable bowel syndrome but the dose and strain needed for benefit is not clear. Of the products available in Australia, the strains and doses are too varied to provide a meaningful recommendation based on evidence.28
There are many psychological therapies that have been shown to improve or resolve symptoms in irritable bowel syndrome. These include cognitive behavioural therapy, multi-component psychological therapy and dynamic psychotherapy.26
Some patients recognise that their symptoms arise or are aggravated by stress and anxiety. For these patients, offering psychological therapies as a direct method to treat irritable bowel syndrome is a reasonable solution. A carefully timed and formulated referral to a psychologist with expertise in functional gastrointestinal disorders improves the chance of a successful outcome.29
Many patients do not associate their symptoms with psychological disturbance, even if there appears to be an obvious clinical correlation. Offering psychological therapy for these people is unlikely to be therapeutic.
Hypnotherapy has been proven to reduce symptoms of irritable bowel syndrome with sustained benefit for greater than five years.30 A recent Australian trial showed that gut-directed hypnotherapy is as effective as a low-FODMAP diet.31
Patients should be advised that hypnosis is not as theatrical as it is portrayed in popular culture. It usually incorporates cognitive behavioural therapy and relaxation exercises administered by a psychologically trained hypnotherapist, typically over 10 weekly sessions.
Physical and behavioural therapies
Pelvic floor dysfunction is underdiagnosed among patients with irritable bowel syndrome, especially those with the constipation subtype.32 These patients either fail to relax the pelvic floor or paradoxically contract the pelvic floor muscles causing obstructed defaecation.33 Through a technique referred to as biofeedback, physiotherapists with expertise can retrain patients to use their pelvic floor muscles appropriately. Patients are given visual or tactile awareness of involuntary bowel function in order to learn voluntary control.34 Behavioural aspects that contribute to symptoms such as incorrect toileting posture, prolonged time spent in the toilet and the use of inappropriate cues to trigger the need to defecate are also addressed with exercises and biofeedback.35 Selecting patients for this therapy is best determined by specialists with expertise in the diagnosis of irritable bowel syndrome.
Some patients can present with a severe form of irritable bowel syndrome, resulting in multiple admissions to hospital and repeated investigations.15 Despite what may appear to be debilitating symptoms, clinicians should avoid prescribing opioids for pain as it can cause narcotic bowel syndrome. These patients are best managed by a single gastroenterologist working with a multidisciplinary team including a psychologist.6
Irritable bowel syndrome is a common chronic gastrointestinal condition. A positive clinical diagnosis is made using the Rome criteria, in the absence of red flags. Patients with red flags should be referred for further testing or specialist assessment.
Once the diagnosis is made, consultations should provide reassurance in an empathetic manner with time allocated to address the patient’s concerns. There are multiple therapeutic modalities that benefit patients with irritable bowel syndrome, including medicines, diet and psychologically based therapies.
Conflict of interest: none declared
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- Pare P, Gray J, Lam S, Balshaw R, Khorasheh S, Barbeau M, et al. Health-related quality of life, work productivity, and health care resource utilization of subjects with irritable bowel syndrome: baseline results from LOGIC (Longitudinal Outcomes Study of Gastrointestinal Symptoms in Canada), a naturalistic study. Clin Ther 2006;28:1726-35.
- Chang JY, Locke GR 3rd, McNally MA, Halder SL, Schleck CD, Zinsmeister AR, et al. Impact of functional gastrointestinal disorders on survival in the community. Am J Gastroenterol 2010;105:822-32.
- Nørgaard M, Farkas DK, Pedersen L, Erichsen R, de la Cour ZD, Gregersen H, et al. Irritable bowel syndrome and risk of colorectal cancer: a Danish nationwide cohort study. Br J Cancer 2011;104:1202-6.
- Irvine AJ, Chey WD, Ford AC. Screening for celiac disease in irritable bowel syndrome: an updated systematic review and meta-analysis. Am J Gastroenterol 2017;112:65-76.
- DiGiacomo D, Santonicola A, Zingone F, Troncone E, Caria MC, Borgheresi P, et al. Human leukocyte antigen DQ2/8 prevalence in non-celiac patients with gastrointestinal diseases. World J Gastroenterol 2013;19:2507-13.
- Cash BD, Chey WD. Irritable bowel syndrome - an evidence‑based approach to diagnosis. Aliment Pharmacol Ther 2004;19:1235-45.
- Turvill J. High negative predictive value of a normal faecal calprotectin in patients with symptomatic intestinal disease. Frontline Gastroenterol 2012;3:21-8.
- Chey WD, Nojkov B, Rubenstein JH, Dobhan RR, Greenson JK, Cash BD. The yield of colonoscopy in patients with non-constipated irritable bowel syndrome: results from a prospective, controlled US trial. Am J Gastroenterol 2010;105:859-65.
- Canavan C, West J, Card T. Review article: the economic impact of the irritable bowel syndrome. Aliment Pharmacol Ther 2014;40:1023-34.
- Eswaran SL, Chey WD, Han-Markey T, Ball S, Jackson K. A randomized controlled trial comparing the low FODMAP diet vs. modified NICE guidelines in US adults with IBS-D. Am J Gastroenterol 2016;111:1824-32.
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- Ford AC, Moayyedi P, Lacy BE, Lembo AJ, Saito YA, Schiller LR, et al. American College of Gastroenterology monograph on the management of irritable bowel syndrome and chronic idiopathic constipation. Am J Gastroenterol 2014;109:Suppl 1:S2-26;quiz S27.
- Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 2014;146:67-75.e5.
- Johannesson E, Simrén M, Strid H, Bajor A, Sadik R. Physical activity improves symptoms in irritable bowel syndrome: a randomized controlled trial. Am J Gastroenterol 2011;106:915-22.
- Siah KT, Wong RK, Ho KY. Melatonin for the treatment of irritable bowel syndrome. World J Gastroenterol 2014;20:2492-8.
- Ruepert L, Quartero AO, de Wit NJ, van der Heijden GJ, Rubin G, Murris JW. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev 2011:CD003460.
- Tack J, Fried M, Houghton LA, Spicak J, Fisher G. Systematic review: the efficacy of treatments for irritable bowel syndrome--a European perspective. Aliment Pharmacol Ther 2006;24:183-205.
- Camilleri M, Boeckxstaens G. Dietary and pharmacological treatment of abdominal pain in IBS. Gut 2017;66:966-74.
- Khanna R, MacDonald JK, Levesque BG. Peppermint oil for the treatment of irritable bowel syndrome: a systematic review and meta-analysis. J Clin Gastroenterol 2014;48:505-12.
- Ford AC, Quigley EM, Lacy BE, Lembo AJ, Saito YA, Schiller LR, et al. Effect of antidepressants and psychological therapies, including hypnotherapy, in irritable bowel syndrome: systematic review and meta-analysis. Am J Gastroenterol 2014;109:1350-65.
- Pimentel M, Lembo A, Chey WD, Zakko S, Ringel Y, Yu J, et al.; TARGET Study Group. Rifaximin therapy for patients with irritable bowel syndrome without constipation. N Engl J Med 2011;364:22-32.
- Chey WD. Symposium report: An evidence-based approach to IBS and CIC: applying new advances to daily practice. A review of an adjunct clinical symposium of the American College of Gastroenterology Meeting October 16, 2016, Las Vegas, Nevada. Gastroenterol Hepatol 2017;13(2 Suppl 1):1-16.
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- Miller V, Carruthers HR, Morris J, Hasan SS, Archbold S, Whorwell PJ. Hypnotherapy for irritable bowel syndrome: an audit of one thousand adult patients. Aliment Pharmacol Ther 2015;41:844-55.
- Peters SL, Yao CK, Philpott H, Yelland GW, Muir JG, Gibson PR. Randomised clinical trial: the efficacy of gut-directed hypnotherapy is similar to that of the low FODMAP diet for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther 2016;44:447-59.
- Suttor VP, Prott GM, Hansen RD, Kellow JE, Malcolm A. Evidence for pelvic floor dyssynergia in patients with irritable bowel syndrome. Dis Colon Rectum 2010;53:156-60.
- Rao SS, Bharucha AE, Chiarioni G, Felt-Bersma R, Knowles C, Malcolm A, et al. Anorectal disorders. Gastroenterology 2016;150:1430-42.e4.
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