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Constipation in Adults

This PatientPlus article is written for healthcare professionals so the language may be more technical than the condition leaflets. You may find the abbreviations list helpful.

What is constipation?

Constipation is a symptom not a diagnosis and means different things to different people. Always ask patients exactly what they mean by the term constipation. There are various formal (and different) definitions of constipation. It is defined as defecation that is unsatisfactory because of infrequent stools (<3 times weekly), difficult stool passage (with straining or discomfort), or seemingly incomplete defecation. Stools are often dry and hard, and may be abnormally large or abnormally small.1

Patients may mean that:

  • Faeces are too hard.
  • They do not defecate often enough for 'inner cleanliness'.
  • Defecation hurts.
  • They have diarrhoea.

Causes of constipation

Taking a careful history helps to determine the possible cause. Ask about frequency, nature and consistency of the stool. Is there blood or mucus in/on the stools? Is there diarrhoea alternating with constipation? Has there been a recent change in bowel habit? Ask about diet and drugs.

Rectal examination is essential.

Causes of Constipation
Common CausesLow-fibre diet.
Inadequate fluid intake or dehydration.
Immobility (or lack of exercise).
Irritable bowel syndrome.
Old age.
Postoperative pain.
Hospital environment (lack of privacy, having to use a bedpan).
Anorectal DiseaseAnal fissure.
Anal stricture.
Rectal prolapse.
Intestinal ObstructionStrictures (e.g. Crohn's disease).
Colorectal carcinoma.
Pelvic mass (e.g. fetus, fibroids).
Diverticulosis (rectal bleeding is a more common presentation).
Congenital abnormalities.
Pseudo-obstruction.
Metabolic/EndocrineHypothyroidism.
Hypercalcaemia.
Hypokalaemia.
Porphyria.
Lead poisoning.
DrugsOpiate analgesics (e.g. morphine, codeine).
Anticholinergics (tricyclics, phenothiazines).
Iron.
NeuromuscularSpinal or pelvic nerve injury.
Aganglionosis (Chagas' disease, Hirschsprung's Disease).
Systemic sclerosis.
Diabetic neuropathy.
Other CausesChronic laxative abuse (rare - diarrhoea is more common).
Idiopathic slow transit.
Idiopathic megarectum/colon.

Investigations

  • Most constipation does not need investigation, especially young, mildly affected patients.
  • Indications for investigation include:
    • Age >40 years.
    • A recent change in bowel habit.
    • Associated symptoms (weight loss, rectal bleeding, mucous discharge, or tenesmus).
  • Possible investigations include:
    • Blood tests: FBC, U&E, Ca2+, TFTs.
    • Sigmoidoscopy and biopsy of abnormal and normal mucosa.
    • Barium enema if there is suspected colorectal malignancy.
    • Special investigations (e.g. transit studies, anorectal physiology) which are occasionally indicated.

Management

  • Treat the cause.
  • Mobilise the patient.
  • Consider drugs only if above measures fail.
  • Try to use drugs for short durations only.

Drug therapy

Drugs for Constipation
Bulk producers:
  • Increase faecal mass, which stimulates peristalsis.
  • They must be taken with plenty of fluid
  • Contra-indications: difficulty in swallowing; intestinal obstruction; colonic atony; faecal impaction.
Examples:
  • Bran powder 3.5 g 2-3 times/day with food.
  • Ispaghula husk, e.g. Fybogel® 3.5 g sachet in water after meals.
  • Methylcellulose, e.g. Celevac® 3-6 500 mg tablets/12-hourly with water.
  • Sterculia, e.g. Normacol® 7 g sachets 1-2 sachets in water once or twice a day after meals.
Stool softeners:
  • Side-effects can include: anal seepage, lipoid pneumonia, malabsorption of fat-soluble vitamins.
  • Arachis oil enemas lubricate and soften impacted faeces.
  • Liquid paraffin should not be used for a prolonged period.
Stimulants:
  • Increase intestinal motility and should not be used in intestinal obstruction.
  • Prolonged use should be avoided as it may cause colonic atony and hypokalaemia (but there are no good, long-term follow-up studies).
  • Pure stimulant laxatives are bisacodyl tablets (5-10 mg at night) or suppositories (10 mg in the mornings) and senna (2-4 tablets at night).
  • Docusate sodium and dantron have stimulant and softening actions; however, dantron is associated with colonic and liver tumours in animals - so reserve its use for the very elderly and the terminally ill.
  • Glycerol suppositories act as a rectal stimulant.
  • Sodium picosulfate is useful for rapid bowel evacuation prior to procedures.
Osmotic agents:
  • Retain fluid in the bowel.
  • Lactulose, a semisynthetic disaccharide, produces an osmotic diarrhoea of low faecal pH that discourages growth of ammonia-producing organisms. It is useful in constipation (dose: 15 mL/12-hourly) and hepatic encephalopathy (dose: 30-50 mL/12-hourly).
  • Magnesium salts (e.g. magnesium hydroxide and magnesium sulphate) are useful when rapid bowel evacuation is required.
Enemas and suppositories - useful additional treatment.
  • Sodium phosphate enemas and glycerin suppositories may be useful.
  • Sodium salts (e.g. Micolette® and Micralax® enemas) should be avoided as they may cause sodium and water retention.
  • Phosphate enemas are useful for rapid bowel evacuation prior to procedures.
  • Excessive use of soapy tap water enemas may lead to water intoxication.
Cost
  • Cheap: senna, bran, co-danthrusate, bisacodyl.
  • Moderate: magnesium hydroxide, methylcellulose, ispaghula granules, sterculia.
  • Expensive: lactulose.

Constipation in children

This is covered in the separate article Constipation in Childhood.

Document references

  1. Constipation, Clinical Knowledge Summaries (January 2008)

Internet and further reading

Acknowledgements

EMIS is grateful to Dr Richard Draper for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2010.
Document ID: 2001
Document Version: 21
Document Reference: bgp841
Last Updated: 13 Aug 2010
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