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Aetiology of constipation

  • General:
    • Poor diet (lack of fibre)
    • Dehydration
    • Immobility
    • Pain (especially post-operative)
  • Medication
    • Opiates
    • Calcium channel blockers (Verapamil)
    • Anticholinergics (Tricyclic antidepressants, phenothiazines)
    • Iron supplements
  • Anorectal disease
    • Anal fissure
    • Rectal prolapse
  • Irritable bowel syndrome
  • Metabolic
    • Hypercalcaemia
    • Hypothyroidism
    • Hypokalaemia
  • Intestinal obstruction
    • Colorectal carcinoma
    • Strictures (Crohn’s)
    • Diverticular disease
  • Slow bowel transit/motility disorders
  • Neuromuscular
    • Nerve injury/trauma
    • Systemic sclerosis
    • Aganglionosis (Chagas’ disease, Hirschprung’s disease)
  • Psychological
    • Different environment
    • Previous trauma/abuse


History in constipation

  • Presenting complaint
    • Infrequent passage of stool (< 3x weekly)
  • History of presenting complaint
    • Frequency, nature and consistency of stool
    • Pain on defecation
    • Straining or discomfort
    • Recent change in bowel habit
    • Constipation alternating with diarrhoea
    • Any associated blood or mucus
    • Tenesmus (sensation of incomplete evacuation on defecation)
    • Abdominal pain
    • Systemic features
  • Past medical history
    • Previous bowel surgery
    • Inflammatory bowel disease
  • Medications
    • See list of causes
  • Allergies
  • Family history
    • Colorectal carcinoma
  • Social history
    • Diet
    • Smoking
    • Psychological history


Examination of constipation

  • Most examinations will be normal
  • Lymphadenopathy, abdominal mass, anaemia would be suspicious for colorectal carcrinoma
  • Digital rectal examination is essential: look for fissures/haemorrhoids, impacted stool, blood/mucus


Initial management of constipation

  • Most patients present with mild symptoms and need little more than taking a thorough history and a proper examination.
  • Blood tests:
    • FBC, Calcium, U+Es (dehydration), Thyroid function tests
  • Abdominal X-ray (often performed in hospital to rule out obstruction)
  • The management for most patients will be reassurance plus advice to eat plenty of fibre and keep well hydrated.
  • Laxatives can be used for mild-moderate symptoms if general measures do not work:
    • Bulking agents e.g. Bran, Ispaghula hulk, methycellulose
    • Stimulant laxatives e.g. Senna (2 tablets/7.5mg at night), Bisacodyl, glycerol suppositories, docusate sodium (also has softening properties, up to 500mg daily in divided doses)
    • Stool softeners e.g. arachis oil enemas, liquid paraffin
    • Osmotic laxatives e.g. Lactulose (initially 10-15 ml twice daily but can be increased, especially in hepatic encephalopathy), phosphate enemas (useful if faecal impaction present or pre-endoscopy)


Further management of constipation

  • A few patients will need further investigation and support.
  • Colonoscopy and biopsies
  • Barium enema
  • CT abdomen
  • Bowel transit studies
  • Anorectal physiology studies
  • Behaviour therapy



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