• Irritable bowel syndrome (IBS) is a chronic, relapsing, and often lifelong disorder of gastrointestinal function with no discernible structural or biochemical cause.
• IBS is characterized by:
• The presence of abdominal pain/discomfort associated with, or relieved by, defecation.
• A change in bowel habit, with constipation, diarrhoea, or both constipation and diarrhoea.
• Abdominal bloating.
• For more information on diagnosing irritable bowel syndrome and excluding other causes of symptoms, see Diagnosis.

• Assess the type and severity of symptoms.
• Assess the person for the presence of red flag indicators. Red flag indicators in people with features of irritable bowel syndrome are:
• Unintentional and unexplained weight loss.
• Rectal bleeding.
• A change in bowel habit to looser or more frequent stools, persisting for more than 6 weeks, in a person over 60 years of age.
• Abdominal mass.
• Rectal mass.
• Anaemia.
• A family history of bowel or ovarian cancer.
• Inflammatory markers for inflammatory bowel disease.
• Assess the person's diet and nutrition:
• Is there anything in the diet that triggers symptoms?
• Review fibre intake. (What type of fibre and how much?)
• Assess the person's physical activity levels, ideally using the the General Practice Physical Activity Questionnaire (GPPAQ).
• Assess the person's lifestyle and psychological status.
• Have they recently experienced any psychological or physical stress?
• Are they depressed or anxious?

In depth

• Encourage people with irritable bowel syndrome (IBS) to try to identify sources of stress, and discuss ways to create relaxation time.
• Give general advice regarding diet.
• High fibre diets are not recommended for people with IBS.
• Advise the person to adjust their fibre intake according to their symptoms:
• Fibre intake often needs to be reduced in people with IBS. Advise people to reduce their intake of insoluble fibre, such as wholemeal or high-fibre flour and breads, cereals high in bran, and whole grains such as brown rice.
• If more fibre is needed, recommend soluble fibre supplements (e.g. ispaghula) or foods high in soluble fibre (e.g. oats).
• Single food avoidance and exclusion diets should only be undertaken under the supervision of a dietitian.
• Give people with low physical activity levels brief advice and counselling to increase their activity levels.
• Discuss the use of probiotics where appropriate. Advise people who wish to try probiotics to choose one brand and:
• Take them for at least 4 weeks while monitoring the effect.
• Take them at the dose recommended by the manufacturer.

In depth

• Use single drugs or a combination of drugs according to the predominant symptoms of the individual.
• Consider an antispasmodic, alongside dietary and lifestyle advice, for all people with irritable bowel syndrome, and in particular those with pain occurring as spasm.
• For people with constipation, consider treatment with a laxative.
• Bulk-forming laxatives are preferred (e.g. ispaghula or sterculia).
• For people who cannot tolerate a bulk-forming laxative, or who need an additional laxative, offer a macrogol (polyethylene glycol) or a stimulant laxative (for short-term use only).
• Lactulose is not recommended.
• For people with diarrhoea, consider treatment with an antimotility drug.
• Loperamide is the antimotility drug of choice.
• Advise people to adjust the dose of laxative or antimotility drug according to response. The aim is to produce a soft, well-formed stool.
• If symptoms do not respond to first-line treatment, consider a trial of a low dose tricyclic antidepressant e.g. amitriptyline 10 mg at night (for pain relief).
• Review 4 weeks after starting treatment and titrate the dose up if necessary (usual maximum 30 mg at night).
• Continue to review every 6–12 months.
• Consider a selective serotonin reuptake inhibitor if a tricyclic antidepressant has previously been shown to be ineffective.

In depth

• Refer to secondary care anyone who presents with a red flag indicator (see Differential diagnosis).
• Consider referral if there is uncertainty about the diagnosis.
• Refer to a registered dietitian for advice and treatment (including single food avoidance and exclusion diets) if general lifestyle and dietary advice are insufficient by themselves to improve symptoms.
• Consider referral if the person has health-related anxieties that have not been allayed.
• Consider referral for psychological interventions (cognitive behavioural therapy, hypnotherapy, or psychological therapy) for people who do not respond to diet, lifestyle, and drug treatments after 12 months.

In depth