How to manage and treat constipation

Dr Laurence Knott examines the various treatments for constipation

Constipation is generally described as infrequent defaecation and/or the passage of hard lumpy stools. The incidence in the general population is between 12 and 19 per cent.

It is more common in the elderly, in women and in patients with cancer. Most constipation is managed in primary care and rarely needs referral.

Causes of constipation include lifestyle factors such as insufficient fibre or fluid intake, lack of exercise or reduced mobility. It is also associa- ted with a number of diseases (see box right).

Some drugs are known to cause constipation, including analgesics, antacids, antiepileptics, antihistamines, anti-psychotics, antispasmodics, calcium supplements, diuretics, iron supplements and verapamil.

In the elderly, the condition can present as overflow diarrhoea, and in children it may present as faecal soiling.

Underlying conditions
An abdominal examination should be made to search for masses or abdominal hernias. Pelvic examination should be performed in women to rule out a uterine prolapse or rectocoele.

Rectal examination may reveal anal fissure or stenosis or rectal prolapse.

Thyroid function tests should be arranged to exclude myxoedema and urea and electrolytes to rule out electrolyte imbalance.

Patients over 50 should have faecal occult blood tests to look for colonic neoplasm. In patients presenting with acute abdomen a referral may be needed.

Referral for colonoscopy should be considered if red flag symptoms are present in a patient over the age of 50. These are worsening of constipation, blood in the stools,  fever, anorexia, nausea or vomiting.

Colorectal cancer
If constipation is accompanied by rectal bleeding, NICE guidelines on colorectal cancer should be followed.

Repeated straining at stool can lead to haemorrhoids and passage of hard stools can lead to anal fissure, so laxatives should be considered.

Bulk-forming laxatives such as ispaghula act by retaining fluid in the bowel, softening and bulking up the stool, and stimulating peristalsis.

Stimulant laxatives such as docusate sodium act by stimulating colonic nerves and increasing peristalsis. They act within 8–12 hours.

Osmotic laxatives, such as lactulose, act by increasing the amount of fluid held in the bowel. They usually provide relief from constipation within two to four days.

Rectal laxatives may be considered when the above measures fail. Oral laxatives may be continued to encourage regular bowel movement.

Rectal osmotic laxatives are useful for hard impacted stools. Rectal faecal softeners, such as arachis oil enemas, are also useful in faecal impaction. Rectal stimulant laxatives clear stools from the lower rectum.

Glycerine suppositories and docusate sodium enemas help with hard and soft stools, whereas bisacodyl suppositories are for soft stools only. 

Dr Knott is a GP in Enfield

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