“The abnormal passage of loose or liquid stools more than 3 times daily and/or a volume of stool greater than 200g/day.

NB This definition is not one to fit all patients.  Make sure to know what is normal for the patient and what the patient defines as diarrhoea (or any change of bowel habit).

In general, acute diarrhoea is <14 days; persistent is >14 days but <28 days and chronic is >28 days.  There are also different types of diarrhoea:

  • Osmotic diarrhoea
    • Due to the passage of inabsorbable compounds through the GI tract.
      • Stops when the offending compound is no longer ingested (fasting)
      • Usually mild
  • Secretory diarrhoea
    • Due to an increase in bowel secretions (usually of chloride ions) or an inhibition of absorption
      • The former can occur as a result of bacterial toxins e.g. cholera
      • Does not stop on fasting
  • Exudative diarrhoea
    • The presence of blood and pus in the stool
      • Occurs in IBD or severe infections e.g. E coli 0157
  • Inflammatory
    • Inflammatory damage to the GI mucosa causes passive loss of protein/fluid and reduces the ability to reabsorb these
      • A process also seen in conjunction with other diarrhoea types, e.g. as a result of an infectious/inflammatory disease.
  • Other causes may be due to an increase in GI tract motility or functional disease


  • Ask about the presenting symptom (diarrhoea):
    • Define the patient’s normal bowel habit.  What has changed?
    • Was it acute/sudden?
    • Describe the bowel movements
      • Duration from onset and each bout?
      • How often?
        • Do they wake you at night?
      • How much?
      • Consistency? (Watery vs soft)
      • Any mucus? Any blood? (describe both if possible)
        • steatorrhoea
      • Appearance
        • Dark/pale; offensive; floating; shape
          • NB You may use aids like the Bristol stool chart to help
          • 479px-Bristol_stool_chart.svg
  • Ask about other symptoms?
    • Nausea/vomiting
    • Weight loss/ loss of appetite
    • Abdominal pain (if so, can it be relieved- how/when etc)
    • Fever, shakes/rigors, sweating
    • Oral ulcers
    • Joint pain
    • Flatus
    • Visual symptoms
  • Ask about PMHx/RHx
    • Any recurrent problems with diarrhoea?
    • Any IBD?
    • Any immunosuppression?
    • What drugs (prescription or OTC)?
  • Any allergies (particularly food)?
  • Any family history?
    • IBD
  • Any contact history- have you come into contact with anyone with similar symptoms
  • Any travel history?
  • Any dietary history? e.g. buffets/exotic restaurants
  • Any pets?
  • Social history-
    • Drinking, smoking, drug taking
    • Home cirucmstances.


(see here)

Also assess

  • Blood pressure


  • Stool culture
  • Bloods
    • FBC- Check WCC for infection; Hb for any anaemia if bloody diarrhoea present
      • +CRP
    • U&Es- check for electrolyte disturbance (in particular hyponatraemia/hypokalaemia)
    • LFTs- if there is a suggestion of jaundice or liver problems
    • TFT- only really if thyroid dysfunction as suspected contributor
  • Sigmoidoscopy/Colonoscopy +/- biopsy
  • Other investigations e.g. antibody tests, CT scans

Differential Diagnosis

  • Infection- gastroenteritis/colitis; diverticulitis (/diverticular disease)
  • Drugs- allopurinol, antibiotics, digoxin, colchicine, chemotherapy, Mg-containing antacids. metformin, NSAIDs, PPIs, SSRIs, statins, thyroxine
  • Constipation with overflow
  • Inflammatory bowel disease
    • Crohn’s Disease
    • Ulcerative colitis
  • Coeliac disease
  • Lactose intolerance
  • Irritable bowel disease
  • Mesenteric ischaemia
  • Small bowel enteropathy
  • Pancreatitis (chronic)
  • Hyperthyroidism
  • Previous surgery
  • Alcoholism
  • Immunodeficiency
  • Factitious diarrhoea


  • Where possible, manage the underlying cause
  • Patients with suspected infective cause do NOT require antibiotics
  • Antidiarrhoeal drugs include
    • Antimotility drugs (e.g. loperamide (Imodium); opiates)
      • Often used in acute setting to improve symptoms
    • Bulk-forming agents e.g. ispaghula husk, methylcellulose
      • Often used in IBS
    • Antisecretory drugs (e.g. racecadotril) can be used in conjunction with rehydration therapy (NOT in children)
    • anti-spasmodic drugs (e.g. antimuscarinics e.g. atropine/hyoscine) are also occasionally used, particularly if there is associated abdominal cramps with the diarrhoea
  •  Many patients with severe diarrhoea will tend to require parenteral fluids +/- nutrition.  Regular monitoring of U&Es is required to ensure hydration is adequate.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: