Irritable bowel syndrome

Management of this common disorder should include dietary advice, writes Dr Zara Aziz.

Patients may describe a history of abdominal pain and bloating (Photograph: SPL)
Patients may describe a history of abdominal pain and bloating (Photograph: SPL)

Irritable bowel syndrome (IBS) is a common disorder of the large intestine characterised by abdominal cramps, nausea, bloating and a change in bowel habit (diarrhoea, constipation or both).

IBS has been known by many names in the past including mucous colitis or nervous colon. Historically this condition was often attributed to the patient's imagination, and although stress is thought to play a part in its aetiology, it is now recognised as a physiological disorder with its own specific signs and symptoms.

Around one in five people in the UK will suffer from IBS at some point in their lives, with a prevalence of 10-20%.

IBS is twice as common in women compared with men.

1. Diagnosis
There is usually an abnormality in how the large bowel functions but no actual structural reason for this. The aetiology is generally poorly understood but is linked to certain medications, dietary habits and even psychological factors in many patients.

It is hypothesised that there may be overactivity of the nerves of the gut, which is often linked to emotional factors. Infections can also cause the gut to become more sensitive, while excessive antibiotic use can kill harmless gut bacteria.

The challenge in primary care is to establish a quick diagnosis whenever patients present with a range of GI symptoms, and to differentiate IBS symptoms from any red flag conditions.

Patients may tell of a history of abdominal pain, bloating and a change in bowel habit that has occurred over several months. Positive diagnostic criteria for IBS include symptoms that are relieved by defecation or altered bowel frequency and at least two of the following: difficulty in passing stool; bloating; worsening of symptoms after meals; passing of mucus. Symptoms such as nausea, back pain or bladder symptoms may also be present.

2. Tests and referral
Blood tests should be performed and include FBC, ESR or plasma viscosity and antibody testing for coeliac disease, such as tissue transglutaminases. If IBS is suspected, it is not necessary to do tests such as ultrasound, barium enema or endoscopy, faecal occult blood, TFTs or hydrogen breath tests for bacterial overgrowth.

Patients should be referred to secondary care if they have symptoms such as unexplained weight loss, rectal bleeding, family history of bowel or ovarian cancer or a change in bowel habit in patients over 60 years of age to looser (or more frequent) stools and lasting for more than six weeks.

Patients should also be promptly referred if they have anaemia, abdominal/pelvic or rectal mass or raised inflammatory markers.

3. Management
Self-help advice is very important in the management of IBS and includes giving information on dietary and lifestyle changes (see box, below) and/or the use of medications such as antispasmodics or antimotility drugs.

Key points
  • The main symptoms of IBS are abdominal pain, bloating and change in bowel habit.
  • Red flag symptoms include unexplained weight loss, rectal bleeding, change in bowel habit in patients under 60 years of age, family history of bowel/ovarian cancer, anaemia, abdominal/rectal/pelvic mass and raised inflammatory markers.
  • Self-help advice is very important in the management of IBS.
  • Antispasmodics, probiotics, loperamide, laxatives or antidepressants form the main pharmacological therapies.
  • Psychological help and exercise may help patients with refractory symptoms.

Antispasmodics are generally considered safe and usually do not cause side-effects (peppermint can cause heartburn and anal irritation).

They all work in slightly different ways and it is worth trying different ones if one does not work. Antispasmodics should be taken just before mealtimes if symptoms are worsened after food. However, these medicines are not recommended in pregnant women.

Probiotics can help some individuals, although there is no scientific evidence to back their efficacy in IBS. They should be tried at the recommended dose for a trial period of four weeks.

If diet is considered to be a significant causative factor and self-help measures fail, referral to a dietitian should be considered, especially if contemplating an exclusion diet. It may be helpful for the patient to keep a food diary as well.

Loperamide can be used to counteract diarrhoea symptoms, and laxatives, other than lactulose, to manage constipation. However, loperamide itself can cause side-effects, such as abdominal cramps and bloating.

To treat constipation symptoms, doses of laxatives are usually adjusted to obtain soft-formed stool (Bristol Stool Scale type 4).

Low-dose tricyclic antidepressants are second-line agents for abdominal pain symptoms. They work by relaxing the smooth muscle in the intestines. They should be introduced gradually and the dose should usually not exceed 30mg.

SSRIs can be an option if tricyclics are not beneficial. These patients should be regularly reviewed initially, but if stable this can be done at sixto 12-month intervals.

Dietary advice
  • Reduce insoluble fibre (bran).
  • Increase soluble fibre (ispaghula powder, oats, barley).
  • Probiotics at the recommended dose.
  • Aloe vera is not recommended.
  • Eat regularly without long gaps.
  • Reduce caffeine; increase water intake.
  • Avoid sorbitol (artificial sweetener) if diarrhoea.
  • Limit fresh fruit to three portions a day.

4. Psychological intervention
For refractory symptoms (lasting more than 12 months) psychological intervention can be considered, including psychological, cognitive behavioural and hypnotherapies.

These therapies have been found to reduce the perception of pain that many IBS patients experience.

Exercise seems to help to varying degrees. There is no firm evidence to suggest that complementary therapies have any benefits. Aloe vera is not advised because it has been found to cause dehydration and reduce blood sugar levels.

In summary, IBS is a common condition in the developed world and can coexist with other GI conditions. It is often a relapsing and remitting problem, closely linked to emotional and lifestyle factors.

Health professionals can manage IBS in primary care through a holistic approach, regular reviews and good communication with patients.

  • Dr Aziz is a GP in Bristol

Reflect on this article and add notes to your CPD Organiser on MIMS Learning

1. NICE. Irritable bowel syndrome in adults. CG61. February 2008.

2. Reme SE, Stahl D, Kennedy T et al. Mediators of change in cognitive behaviour therapy and mebeverine for irritable bowel syndrome. Psychol Med 2011; 41: 2669-79.

3. CKS. Irritable bowel syndrome - management. Last revised August 2008.

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