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October 2008: Tailor treatment to the patient in irritable bowel syndrome

What dietary changes may help patients with irritable bowel syndrome?

What drug treatments should be considered?

When should patients be referred?

What dietary changes may help patients with irritable bowel syndrome?

What drug treatments should be considered?

When should patients be referred?

Irritable bowel syndrome (IBS) is a chronic disorder that affects around 10-20% of the UK population. It is most common in patients aged 20-30 years, although it may occur in older patients, and is twice as common in women.1

IBS is not just a motility disorder of the colon but a condition that affects the whole length of the gastrointestinal tract. Other factors, such as visceral hypersensitivity; inflammation; heredity; disturbed CNS processing of noxious stimuli from the intestine; diet and psychological influences also contribute to the overall clinical picture.2

In the past, the psychological aspects of the condition have probably been overemphasised.

Stress does not cause IBS, although it affects consultation behaviour and exacerbates the condition.

A good way of understanding IBS is to use the biopsychosocial model of disease,3 which aims to explore the interaction of organic, psychological and social factors in the expression of an illness.

NICE has recently published a guideline on irritable bowel syndrome in adults,1 which aims to improve the diagnosis, investigation and management of the condition.

Symptoms

The principal symptoms of IBS are abdominal pain, which can occur at any site; abdominal bloating, which may be accompanied by an actual increase in girth; and a disturbed bowel habit: about one-third of patients have constipation, one-third diarrhoea and one-third alternate between the two (see table 1, attached). In addition, many patients also complain of non-colonic symptoms, such as low backache, lethargy, nausea and urinary symptoms including frequency or urgency (see table 2, attached).4

Symptoms are often worse during menstruation and women may also experience pain during or after intercourse, sometimes even the following day.5

Diagnosis

IBS should be a positive diagnosis,1 particularly in younger patients, rather than a diagnosis of exclusion.

In many patients the diagnosis is obvious, especially if it is accompanied by bloating, which is almost specific for functional gastrointestinal disorders and typically gets worse throughout the day.

Non-colonic symptoms can cause diagnostic uncertainty and result in inappropriate treatment and investigation.6-8 However, the greater the number of symptoms, the more likely the diagnosis of IBS.9 In some patients the non-colonic symptoms are more intrusive than the gastrointestinal symptoms, and GPs should ask patients who present with tiredness, nausea or low backache about gastrointestinal problems.

Constipation is unlikely to be associated with any serious disease but it is important to ensure it is not caused by concomitant medication. However, diarrhoea may be indicative of conditions such as coeliac disease or inflammatory bowel disease, although the latter is often accompanied by blood in the stools, systemic upset, extraintestinal manifestations and a raised ESR or plasma viscosity (see table 3, below).

41209695The NICE guideline recommends that all patients with suspected IBS should have an FBC, ESR or plasma viscosity, CRP and serological screening for coeliac disease (either endomysial antibodies or tissue transglutaminase).1

41209696Carcinoma of the colon should always be ruled out in patients over 50 or in younger patients with a family history of colon cancer, especially if this occurred at a young age. It is also important to enquire about red flags, such as rectal bleeding, anaemia, weight loss and recent onset of symptoms (see table 4, left).1 This latter feature is particularly useful as most patients with IBS have a long history of gastrointestinal symptoms, even though they may have been very mild and the patient may not have consulted about them.

Treatment

GPs should ensure that all patients understand that IBS is a treatable illness affecting the gut and is not all in the mind. However, patients exposed to excessive ‘malignant' stress, such as an abusive relationship, can be difficult to treat.

Patients often find that eating makes their symptoms worse. The most common component of the diet that can exacerbate the condition is fibre, especially insoluble fibre such as in cereals.10 Patients should therefore be advised to avoid breakfast cereals, brown bread and anything containing brown flour for 8-12 weeks. If there is some response they should be encouraged to continue, and can be reassured that there is very little evidence that removing this component of their diet is harmful.

Other foods can cause problems but these often vary from patient to patient. Problem foods should be identified by a process of trial and error, with the patient excluding only one of the presumed offending foods from their diet for several weeks, and then deciding whether this was beneficial.

If a patient has a good response to cereal withdrawal, reintroduction is not recommended. However, for other foods it is worth testing with reintroduction in case the reduction in symptoms was coincidental.

Antispasmodics can be effective for treating pain and should preferably be used on an as necessary basis. There is a considerable individual variation in response to these drugs and it is well worth trying a variety, as some have an anticholinergic effect, such as hyoscine or dicycloverine, and others act on smooth muscle, for example mebeverine or alverine.

Bowel habit needs to be treated separately from pain. Loperamide is probably the most useful antidiarrhoeal that is safe for long-term treatment. Laxatives such as macrogols do not damage the bowel in any way and should be prescribed at a low dose on a regular basis rather than intermittently, as these doses often have to be larger to clear the backlog and consequently may lead to a more violent effect. Lactulose should be avoided as it tends to cause gas and bloating, which can exacerbate IBS.

If these measures fail the next step is to try antidepressants. This approach is often met with resistance by patients, who may think they are being diagnosed with depression.

Tricyclics, such as amitriptyline, seem to be especially effective11 even at low doses, such as 10-20mg, which suggests that the mechanism of action is not primarily through their antidepressant activity. There is some evidence for a direct effect on the gut as well as on the central processing of pain. Tricyclics can be used in both diarrhoea- and constipation-predominant IBS, and at low doses are unlikely to exacerbate constipation in the latter group of patients.

For those cases that remain refractory to treatment, behavioural therapies such as CBT, hypnotherapy and psychotherapy can be considered. There is evidence that all these therapies are effective,1 but unfortunately there is considerable variation in the provision of such services and the choice is largely dependent on local availability.

Thus there is no single treatment for IBS that suits all patients and the therapeutic approach has to be tailored to the patient's symptoms.

A combination of diet, antispasmodics and laxatives or antidiarrhoeals may be necessary to achieve maximum effect in some patients.

Referral

Patients should be referred to secondary care if there is diagnostic uncertainty or if the patient fails to respond to treatment. The former is more likely in patients with a loose bowel habit, older patients and those with a recent onset of symptoms. Patients with ‘gastroenteritis' can also pose problems as this may be the first manifestation of IBS, and in bacteriologically confirmed dysentery it is not unusual for symptoms to take many weeks to settle down.

Patients who fail to respond to treatment generally have refractory IBS but in some cases the diagnosis may have been incorrect.

Some patients may be reluctant to accept a diagnosis of IBS without a specialist opinion and investigation. These patients should be referred to secondary care, as it is often impossible to move forward with management until the patient is reassured. .

Tailor treatment to the patient in irritable bowel syndrome Key points Table 1: Symptoms of IBS Table 2: Non-colonic symptoms of IBS IBS_tab3 IBS_tab4 Authors

Dr C Shekhar
MB BS MRCP
clinical research fellow

Professor Peter J Whorwell
MD PhD FRCP
Professor of Medicine and Gastroenterology, Wythenshawe Hospital, Manchester

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