Irritable Bowel Syndrome

oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Irritable bowel syndrome (IBS) is a relapsing functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit. Bloating and distension are often associated. IBS is defined by symptom-based diagnostic criteria, in the absence of detectable organic causes. The symptoms are not specific for IBS.[1] The diagnosis of IBS rarely alters over time, but always be prepared to reconsider the diagnosis if the clinical picture changes. IBS has a significant negative impact on quality of life and social functioning in many patients, but it is not associated with the development of serious disease or with excess mortality.[2] Although still considered as a functional disorder, there is increasing evidence that organic disease of the gastrointestinal (GI) tract (eg subtle inflammatory bowel disease (IBD), serotonin dysregulation, bacterial overgrowth and central dysregulation) can be identified in subsets of patients.[3]

  • IBS is the most common functional GI disorder; the one year prevalence is about 19% but only a third present to their GPs.[4]
  • If the strict Rome III criteria for IBS are used,[5] it affects around 5-11% of individuals, with similar prevalence in developed or developing countries.[6]
  • IBS may present at any age (peak prevalence in 30s and 40s - female predominance is most obvious in the 3rd decade and declines afterwards).[6]
  • Symptoms may emanate from the whole gut rather than just the colon.
  • There is no structural lesion, but it may be explained by abnormal smooth muscle activity ± visceral hypersensitivity (there appears to be an association with bronchial hyper-responsiveness)[7] and abnormal central processing of painful stimuli.
  • There appears to be a significant subgroup of patients in whom IBS is precipitated by an episode of bacterial gastroenteritis (~10% in one study).[8]. They have predominantly diarrhoeal symptoms, less psychiatric illness and increased serotonin-containing enterochromaffin (EC) cells compared with other IBS patients.[9]

National Institute for Health and Clinical Excellence (NICE) positive diagnostic criteria for IBS[10][11]

Patients must give at least a 6-month history of either:
  • Abdominal pain or discomfort.
  • Bloating.
  • Change in bowel habit.
Consider positively diagnosing IBS only if abdominal pain is either relieved by defecation, or associated with altered bowel frequency or stool form;
AND at least 2 of the following are present:
  • Altered passage of stool (straining, urgency, incomplete evacuation).
  • Abdominal bloating (women >men), distention tension or hardness.
  • Symptoms aggravated by eating.
  • Passage of mucus rectally.
Lethargy, nausea, backache and bladder symptoms may be used to support diagnosis.

Patients may have frequent consultations for non-gastrointestinal symptoms and may have a number of previous medically unexplained symptoms.[6]

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Further notes on IBS features

  • Most patients have abdominal pain and disordered bowel habit, continuous or intermittent. This may be predominantly diarrhoea, predominantly constipation, or alternating between the two. A 'morning rush' is common: patients feel the urgent need to defecate several times on getting up, during and after breakfast.
  • Symptoms are chronic, with remissions interrupted by relapses precipitated by stress or changes in bowel flora produced by antibiotics.
  • Symptoms may begin following an episode of gastroenteritis.[9]
  • Upper GI symptoms may include nausea, heartburn, dysphagia, and early satiety.
  • Extra-intestinal symptoms such as headaches and migraine, asthma, backache, lethargy, dyspareunia, urinary frequency, and urgency are more commonly reported by patients with IBS. Psychological problems (anxiety and depression) are also more common, although some psychological morbidity appears to be associated with health care-seeking rather than with IBS per se.

Subclasses of IBS[12]

  • Approximately one third of patients have IBS with constipation (IBS-C) = loose stools <25% and hard stools >25% of the time.
  • Approximately one third of patients have IBS with diarrhoea (IBS-D) = loose stools >25% and hard stools <25% of the time.
  • The remainder have IBS-mixed (IBS-M) = both hard and soft stools >25% of the time.


On abdominal examination, signs may be few and nonspecific (eg tender, palpable colon). A rectal ± pelvic examination may be appropriate.

The condition has a considerable impact on quality of life - comparable with type 2 diabetes, ischaemic heart disease or depression.[13]

  • Carefully and sympathetically elicit a history and carry out an appropriately thorough physical examination.
  • Check full blood count and inflammatory markers (C-reactive protein (CRP) and either erythrocyte sedimentation rate (ESR) or plasma viscosity).[10]
  • Serological testing for coeliac disease,[10] particularly in patients with IBS-D, and in areas of high incidence, as this diagnosis is easily missed.
  • Thyroid function tests ± stool culture are not normally indicated but may be appropriate in patients with recent onset IBS-D.
  • Ask about a family history of IBD or colon cancer, at age <50 - as this should lower the threshold for investigation/referral.[6]
  • Lactose intolerance testing (lactose breath hydrogen test) and/or measuring faecal fats (malabsorption?) may be helpful in some cases.

Refer patients when there is diagnostic uncertainty, alarm symptoms, or severe resistant symptoms (eg for more specialist treatments, exclusion diets, etc.). GPs refer about one in seven cases to specialists.

Referral to secondary care[10]

Refer patients with possible IBS for further investigation if any red flag symptoms are present:
Refer patients with possible IBS for further investigation if any red flag signs are present:
  • Anaemia.
  • Abdominal or rectal masses.
  • Raised inflammatory markers (ie may have IBD).

An urgent 2-week referral is occasionally appropriate, eg weight loss, rectal bleeding, jaundice, abdominal mass, etc..

  • Lower bowel investigations - colonoscopy, or sigmoidoscopy ± barium enema. A rectal biopsy may be appropriate (to diagnose IBD bowel disease).
  • Gastroscopy may be appropriate if upper GI symptoms predominate.
  • Gynaecological referral may help rule out endometriosis and pelvic infection.
  • Consider psychological referral if the main problems are inability to cope with symptoms.

Beware of unnecessary specialist referral and interventions, eg hysterectomy and cholecystectomy. Referral may prolong anxiety as much as allay it.

  • Doctors and patients can use Decision Aids together to help choose the best course of action to take.
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Having confidently made the diagnosis, reassurance and explanation are vital, including frank explanation of the likely course of disease. Many patients may have a fear of cancer, but only careful and often repeated explanations of the nature of the disease reduce this.

Lifestyle, diet and physical activity

  • Provide information about self-help, covering lifestyle, physical activity, diet and symptom-targeted medication.
  • Encourage patients to identify and make best use of leisure time, and create times in the day for relaxation.
  • Assess physical activity levels, eg General Practice Physical Activity Questionnaire (GPPAQ), and give advice on increasing activity if appropriate.
  • Give general advice on diet:

General dietary advice[10]

  • Have regular meals - ie avoid long gaps between meals and don't rush them.
  • Drink plenty of fluids (at least 8 cups per day) but restrict tea/coffee to 3 cups or so per day.
  • Reduce intake of alcohol and fizzy drinks.
  • Consider limiting high-fibre foods (eg wholemeal flour or bran), and resistant starches (often in processed or recooked foods, and fresh fruits - limit to 3 portions per day).
  • For diarrhoea - avoid sorbitol.
  • For wind - consider increasing oats and linseeds (one tablespoon/day).

Make a full assessment of psychological and social factors as well as physical symptoms, and management involves directing treatment towards the specific symptoms (diarrhoea etc.) and/or modifying the central appreciation of pain (eg psychotherapy, antidepressants). A two-week symptom diary may be useful in identifying food or stress influences on IBS symptomatology, and may be the first step in effective cognitive behavioural therapy (CBT).[15] Consider using the hospital anxiety and depression scale or Patient Health Questionnaire (PHQ9), or PHQ15, to help assess the level of anxiety or depression.

In people without marked psychiatric abnormalities, consider relaxation therapy, biofeedback, and hypnotherapy. Where there is marked psychiatric illness, CBT, dynamic psychotherapy, and psychiatric referral may be more appropriate.

Food intolerance is common with IBS (33-66%) although true allergies are rare; suggest omitting any known food triggers, but a formal exclusion diet needs the support of a committed dietician.[10][16] Lactose intolerance occurs in ~10%, but a lactose-free diet often has no effects on symptoms.[16] Target the most troublesome symptom (diarrhoea, constipation or abdominal spasm), ideally with 'as required' medication or careful dose titration. Try to manage children by dietary changes alone, as evidence for drug treatment is poorer than in adults, and laxatives are more likely to cause dependence.[17]

  • Constipation-predominant IBS (IBS-C)
    • Encourage patients to eat at regular intervals and increase exercise.
    • Increase dietary insoluble fibre (eg whole grain cereals) and soluble fibre (other cereals, fruit and vegetables) - but be aware that increasing the latter may increase bloating and wind. Ispaghula husk (soluble fibre - bulking agent) has been shown to increase stool frequency (better tolerated than wheat bran) and improves overall symptoms and IBS-related constipation (insoluble fibre only helps the constipation).[18]
    • Supplement if necessary with an osmotic laxative (eg lactulose or magnesium hydroxide) or stool softener (liquid paraffin) - avoid stimulant laxatives (these can cause cramping pains).
    • Selective serotonin 4 (5-HT4) receptor agonists (eg tegaserod) have prokinetic activity and are licensed in many parts of the world for short-term use in IBS-C. They appear to improve overall symptomatology, but there are few data on their effect on quality of life.[19]
  • Diarrhoea-predominant IBS (IBS-D)
    • Symptoms may respond to low-fat diet, reduced caffeine intake and stopping smoking.
    • Some fibre helps - but the patient may need to reduce a particularly high fibre intake. Excessive supplements (eg vitamin C or magnesium) can also cause diarrhoea, as can a high fructose intake in some individuals.
    • Loperamide (opioid analogue) reduces stool frequency and urgency, and improves stool consistency without the sedation and drug dependency of codeine. Titrate the dose carefully to avoid constipation.
    • Low-dose tricyclic antidepressants help pain,[20] and, as they also tend to cause constipation, they may have particular benefit in IBS-D.
    • 5-HT3 receptor antagonists (eg ondansetron) are being developed.
  • Abdominal spasms
    • Smooth muscle relaxants (eg mebeverine and alverine) appear to improve global rating of symptoms and reduce pain in IBS patients.[20] They have relatively few adverse effects but only benefit some patients.
    • Antimuscarinics (hyoscine and dicycloverine) are occasionally helpful, but anticholinergic side-effects limit use.
    • Peppermint oil is commonly recommended as a smooth muscle relaxant It may help symptoms of abdominal pain, distension, and stool frequency (more evidence is needed).[16]
    • Transcutaneous electrical nerve stimulation (TENS) may be effective for pain, but usually has no effect on other symptoms.

Other therapies

  • Low-dose tricyclic antidepressants may be effective in reducing pain.[20] If depression is a feature a standard antidepressive dose may be appropriate[21] - tricyclics tend to constipate and selective serotonin reuptake inhibitors (SSRIs) may cause diarrhoea. NICE recommends trying tricyclics before SSRIs.[10]
  • Only use tranquillisers (eg diazepam) if symptoms are stress-related; and then only use short-term.
  • Chinese herbal medicine has been used with success[22] (as long as drugs like aristolochia, stephania and clematis are avoided). A recent randomised controlled trial has shown a commercially available herbal preparation containing nine plant extracts (STW 5) is effective in reducing symptoms in IBS (as was a research herbal preparation (STW 5-II) containing six plant extracts).[23]
  • Short-term therapy with probiotics such as Lactobacillus plantarum (LP01) and Bifidobacterium breve (BR0) shows some benefit in reducing symptoms, but more research is needed.[24] If a patient wants to try these - take only the recommended dose for at least 4 weeks while monitoring effects.[10]
  • New drugs, such as cholecystokinin, neurokinin, and corticotropin receptor antagonists are being developed.
  • Aloe vera is not recommended.[10]
  • More than 50% will continue to have symptoms after 5 years.
  • IBS is not associated with the long-term development of any serious disease, although IBS patients are more likely to undergo certain surgical operations (eg hysterectomy or cholecystectomy) than controls.[25]
  • Patients with a long history are less likely to improve.
  • The postinfective subgroup appears to have a better prognosis, with symptoms resolving within 6 years in about half of patients.[8]

Further reading & references

  1. Irritable bowel syndrome: a global perspective; World Gastroenterology Organisation Global Guideline, April 2009
  2. Guidelines on the Irritable Bowel Syndrome: Mechanisms and Practical Management; British Society of Gastroenterology (May 2007)
  3. Talley NJ; Irritable bowel syndrome. Intern Med J. 2006 Nov;36(11):724-8.
  4. Jones R, Lydeard S; Irritable bowel syndrome in the general population. BMJ. 1992 Jan 11;304(6819):87-90.
  5. Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders
  6. Spiller R, Aziz Q, Creed F, et al; Guidelines for the management of Irritable Bowel Syndrome. Gut. 2007 May 8;.
  7. Kennedy TM, Jones RH, Hungin AP, et al; Irritable bowel syndrome, gastro-oesophageal reflux, and bronchial hyper-responsiveness in the general population. Gut. 1998 Dec;43(6):770-4.
  8. Neal KR, Barker L, Spiller RC; Prognosis in post-infective irritable bowel syndrome: a six year follow up study. Gut. 2002 Sep;51(3):410-3.
  9. Dunlop SP, Jenkins D, Spiller RC; Distinctive clinical, psychological, and histological features of postinfective irritable bowel syndrome. Am J Gastroenterol. 2003 Jul;98(7):1578-83.
  10. Irritable bowel syndrome; NICE Clinical Guideline (February 2008)
  11. Dalrymple J, Bullock I; Diagnosis and management of irritable bowel syndrome in adults in primary care: summary of NICE guidance. BMJ. 2008 Mar 8;336(7643):556-8.
  12. Spiller R; Clinical update: irritable bowel syndrome. Lancet. 2007 May 12;369(9573):1586-8.
  13. Hahn BA, Yan S, Strassels S; Impact of irritable bowel syndrome on quality of life and resource use in the United States and United Kingdom. Digestion. 1999 Jan-Feb;60(1):77-81.
  14. O'Leary C, Wieneke P, Buckley S, et al; Celiac disease and irritable bowel-type symptoms. Am J Gastroenterol. 2002 Jun;97(6):1463-7.
  15. Guthrie E, Creed F, Dawson D, et al; A controlled trial of psychological treatment for the irritable bowel syndrome. Gastroenterology. 1991 Feb;100(2):450-7.
  16. Gunn MC, Cavin AA, Mansfield JC; Management of irritable bowel syndrome. Postgrad Med J. 2003 Mar;79(929):154-8.
  17. Irritable bowel syndrome, Prodigy (August 2008)
  18. Bijkerk CJ, Muris JW, Knottnerus JA, et al; Systematic review: the role of different types of fibre in the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2004 Feb 1;19(3):245-51.
  19. Evans BW, Clark WK, Moore DJ, et al; Tegaserod for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2004;(1):CD003960.
  20. Poynard T, Regimbeau C, Benhamou Y; Meta-analysis of smooth muscle relaxants in the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2001 Mar;15(3):355-61.
  21. O'Malley PG, Jackson JL, Santoro J, et al; Antidepressant therapy for unexplained symptoms and symptom syndromes. J Fam Pract. 1999 Dec;48(12):980-90.
  22. Bensoussan A, Talley NJ, Hing M, et al; Treatment of irritable bowel syndrome with Chinese herbal medicine: a randomized controlled trial. JAMA. 1998 Nov 11;280(18):1585-9.
  23. Madisch A, Holtmann G, Plein K, et al; Treatment of irritable bowel syndrome with herbal preparations: results of a double-blind, randomized, placebo-controlled, multi-centre trial. Aliment Pharmacol Ther. 2004 Feb 1;19(3):271-9.
  24. Saggioro A; Probiotics in the treatment of irritable bowel syndrome. J Clin Gastroenterol. 2004 Jul;38(6 Suppl):S104-6.
  25. Kennedy TM, Jones RH; Epidemiology of cholecystectomy and irritable bowel syndrome in a UK population. Br J Surg. 2000 Dec;87(12):1658-63.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Huw Thomas
Current Version:
Peer Reviewer:
Dr Helen Huins
Last Checked:
Document ID:
2854 (v24)