Irritable bowel syndrome

Irritable bowel syndrome is a common lifelong condition affecting the gastrointestinal tract, causing diarrhoea and/or constipation as well as abdominal pain and discomfort (National Institute for Health and Care (NICE), 2017). Pain is often relieved by defaecation. Irritable bowel syndrome is characterised by periods when the person is well with periodic relapses (Snyder, 2023).

Twice as many women are affected by irritable bowel syndrome compared to men, and it affects between 10-20% of the general adult population (NICE, 2017).

The symptoms of irritable bowel syndrome vary between individuals, but generally include:

• abdominal pain (often worse after eating and relieved by defaecation)
• bloating (abdominal distension)
• diarrhoea, including:
  • watery stool
  • urgency
  • frequency
• constipation (NICE, 2017)

Some people are affected by diarrhoea more than constipation and sometimes this is classified as diarrhoea-predominant irritable bowel syndrome. Diarrhoea-predominant irritable bowel syndrome is characterised by at least one-quarter of stools being loose or watery and less than one-quarter being hard or lumpy.

Others are more affected by constipation and sometimes this is classified as constipation-predominant irritable bowel syndrome. Constipation-predominant irritable bowel syndrome is characterised by at least one-quarter of stools being hard or lumpy and less than one-quarter being loose or watery.

Most people who have irritable-bowel syndrome are affected by both types at some stage; this is called irritable bowel syndrome with mixed bowel habit. Irritable bowel syndrome with mixed bowel habit is characterised by

The cause of irritable bowel syndrome is not known, but it is likely that multiple causes that give rise to different symptoms and different intensity of symptoms are responsible (Snyder, 2023). There is some evidence of a familial link to irritable bowel syndrome (NICE, 2023).

Approximately 10% of people with irritable bowel syndrome will have developed it following an acute intestinal infection, while others may have a history of another inflammatory bowel condition. Other causes might arise from the individual’s diet, including alcohol use and their antibiotic history (NICE, 2023).

There is evidence that some people experience worse symptoms of irritable bowel syndrome when they are stressed and this is triggered by psychological activity affecting the gut via the brain-gut axis. There is emerging evidence that psychological therapies and the use of antidepressants in some people might lead to an improvement in symptoms by addressing the signals from the brain

The diagnosis of irritable bowel syndrome is based on symptoms and exclusion of other causes (NICE, 2016). Irritable bowel syndrome is usually diagnosed in primary care settings, where the GP will question the person about their bowel habit, signs and symptoms and whether the person noticed any foods which triggered an episode. The GP will consider the ABC of irritable bowel syndrome:

• abdominal pain
• bloating
• change in bowel habit (NICE, 2023)

These symptoms should have been present for over 6 months and may be relieved by defaecation or accompanied by altered frequency of bowel opening and other signs and symptoms described earlier (NICE, 2017).

It is important to exclude issues such as coeliac disease (determined using a blood test of a patient after having eaten wheat) and tests on a sample of faeces for other inflammatory bowel disease (NICE, 2016), as well as bowel cancers, especially in people over the

There is no cure for irritable bowel syndrome, but the symptoms can be managed through changes to the diet and some medications. The NHS (2021) recommends lifestyle changes for people newly diagnosed with irritable bowel syndrome to reduce their symptoms; these include:

• cooking with fresh ingredients
• keeping a food and symptom diary to identify what foods trigger symptoms
• taking part in relaxation activities
• exercising regularly
• taking probiotics
• avoiding skipping meals
• eating slowly
• avoiding fatty, spicy or processed food
• eating less than three portions of fresh fruit a day
• drinking less than three caffeinated drinks a day
• drinking less alcohol or fizzy drinks

If initial general lifestyle and dietary advice does not help to reduce the symptoms, then people should be offered further dietary management (NICE, 2016). There is evidence from systematic reviews and within the British Dietetic Association guidelines that further dietary management should be offered via a dietitian and

Nursing and Midwifery Council: standards of proficiency for registered nurses

Part 1: Procedures for assessing people’s needs for person-centred care

1. Use evidence-based, best practice approaches to take a history, observe, recognise and accurately assess people of all ages

Part 2: Procedures for the planning, provision and management of person-centred nursing care

5. Use evidence-based, best practice approaches for meeting needs for care and support with nutrition and hydration, accurately assessing the person’s capacity for independence and self-care and initiating appropriate interventions

6. Use evidence-based, best practice approaches for meeting needs for care and support with bladder and bowel health, accurately assessing the person’s capacity for independence and self-care and initiating appropriate interventions

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Gracie DJ, Hamlin PJ, Ford AC. The influence of the brain–gut axis in inflammatory bowel disease and possible implications for treatment. Lancet Gastroenterol Hepatol. 2019;4(8):632-642. https://doi.org/10.1016/S2468-1253(19)30089-5 

Ianiro G, Eusebi LH, Black CJ et al. Systematic review with meta-analysis: efficacy of faecal microbiota transplantation for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2019;50:240–248. https://doi.org/10.1111/apt.15330 

Jalili M, Vahedi H, Poustchi H et al. Effects of vitamin D supplementation in patients with irritable bowel syndrome: a randomized, double-blind, placebo-controlled clinical trial. Int J Prev Med. 2019;10:16. https://doi.org/10.4103/ijpvm.IJPVM_512_17 

Khayyat Y, Attar S. Vitamin D deficiency in patients with irritable bowel syndrome: does it exist? Oman Med J. 2015;30(2):115-8. https://doi.org/10.5001/omj.2015.25 

McKenzie YA, Bowyer RK, Leach H et al. British Dietetic Association systematic review and evidence-based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update). J Hum Nutr Diet. 2016;29(5):549-75.