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in adults

Constipation is a common disorder with a prevalence of 10-20 per cent in Western countries.

Traditionally the treatment of constipation has been centred on increasing fluid intake and fibre in the diet and promoting exercise followed by the use of laxatives/ bulking agents.

However, is there any evidence to support this strategy ­ and which works best? Two excellent review articles published in the last year assess the evidence1,2.

What works?

Three small RCTs showed an improvement in stool frequency and consistency with ispaghula husk (psyllium) compared with placebo. There is no reliable data to support the use of wheat bran or methylcellulose in the treatment of constipation.

Four well-designed RCTs showed polyethylene glycols (eg Movicol) to be superior to placebo at improving stool frequency and consistency. Although there were five RCTs showing lactulose to be superior to placebo it compared less favourably against both psyllium and polyethylene glycol and was associated with more side-effects, particularly bloating.

What doesn't work?

Neither review article found any evidence that a high-fibre diet, increased fluids or exercise improved chronic constipation. The effect of these interventions on milder symptoms was not commented upon.

There is insufficient evidence to suggest the use of stool softeners is beneficial in chronic constipation, as most of the trial data comes from poorly designed studies with small sample sizes and diverse populations. Docusate is included in this category, as it possesses softening as well as stimulant properties.

There are no placebo-controlled RCTs assessing stimulant laxatives in the management of constipation. There are several poorly designed studies comparing them with bulking agents and osmotic laxatives, which provide insufficient data to make any reliable conclusions about effectiveness.

Diagnosing constipation

Constipation is more frequent in women and with advancing age. The Rome II criteria3 diagnose chronic constipation as having two or more of the following symptoms for at least 12 weeks in the year:

·straining at defaecation

·passage of hard/lumpy stools

·a feeling of incomplete evacuation and fewer than three bowel movements a week.

The patient may also complain of associated bloating or abdominal pain. Ultimately constipation is defined by the patient's perception of a normal bowel habit rather than diagnostic criteria and most cases seen in primary care are mild with only a short history.

Most patients with simple constipation do not have an underlying organic disorder, but a detailed history and examination (including a rectal examination) should be performed on all patients. The history should pay attention to gastrointestinal, endocrine and neurological symptoms as well as drug therapy. Only patients with alarm symptoms or who do not respond to appropriate therapy should have further investigation.

The bottom line

·Constipation is a common condition with significant morbidity and health care costs.

·Most cases do not have an underlying cause. Those with alarm symptoms or who fail to respond to treatment may need investigation.

·Ispaghula husk and polyethylene glycols are the only treatments shown to have

benefit over placebo and other measures

in trials. It is reasonable to treat patients with ispaghula husk first line and then

polyethylene glycol if there is inadequate response.

·It may be necessary to use a combination of therapies in some patients.

·Ispaghula husk may worsen discomfort if the patient has IBS. Polyethylene glycols are an appropriate first-line in such patients.

·Although evidence for dietary modification, lactulose and stimulant laxatives was weak, this was largely due to poor study design. They may play a part in an individual patient's management, particularly if they do not tolerate the first-line choices.

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