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  • While diarrhoea is commonly infectious, it can also be caused by malabsorption, drugs and other non-gastrointestinal pathologies. 


    • Causes of Diarrhoea

    • Inflammatory

    • Viral infection - rotavirus, norovirus, adenovirus
    • Bacterial infection - Campylobacter, Shigella, Salmonella, Escherichia coli, Clostridium difficile, Vibrio cholerae, Staph aureus
    • Parasitic infection - giardiasis
    • Inflammation - Crohn’s disease, ulcerative colitis, diverticulitis, appendicitis, ischaemic colitis, radiation colitis, colorectal cancer
    • Fatty

    • Malabsorption - lactose / fructose intolerance, coeliac disease, mesenteric ischaemia, short bowel syndrome, amyloidosis, tropical sprue, Whipple disease
    • Exocrine deficiency - cholestasis, pancreatic exocrine insufficiency
    • Watery

    • Medications - laxatives, magnesium, antihypertensives, lipid-lowering meds, PPIs, NSAIDs, antibiotics, certain chemotherapy
    • Endocrine - hyperthyroidism, adrenocortical insufficiency
    • Neuroendocrine tumour - gastrinoma, VIPoma, carcinoid syndrome
    • GI neoplasia - colorectal cancer, lymphoma, villous adenoma
    • Alcohol abuse
    • Functional

    • Irritable bowel syndrome
  • Don't forget to check whether your patient is on laxatives, as this may be a simply treated cause for their diarrhoea.

History of Presenting Complaint

    • Stools

      The frequency, colour and consistency of the patient's stools.
    • Watery stoolsSuggestive of osmotic or secretory cause
    • Steatorrhoea: fatty stools that floatSuggestive of malabsorption or exocrine deficiency
    • Blood-stained stoolsSuggestive of inflammatory cause, e.g. infection, inflammation, ischaemia or tumour
    • High-volume diarrhoeaSuggestive of small bowel pathology
    • Increased frequency of small volume diarrhoeaSuggestive of large bowel pathology
    • Alternating diarrhoea and constipationSuggestive of irritable bowel syndrome (IBS)
    • Triggers

      Whether there was any inciting event prior to onset of the diarrhoea.
    • Post recent tavelSuggestive of infection, especially enterotoxic E coli
    • After eating seafoodSuggestive of Vibrio infection
    • During or after a course of antibioticsPotential Clostridium difficile infection
    • Associated Symptoms

      Whether the diarrhoea is associated with any other symptoms.
    • Nausea / vomitingSuggestive of inflammatory cause, particularly infection
    • Severe abdominal painSuggestive of inflammatory cause
    • FeversSuggestive of infectious cause
    • Weight lossSuggestive of malabsorption or cancer
    • Perianal discharge or fistulaSuggestive of inflammatory bowel disease
    • Severity

    • Whether the patient has been able to keep down any fluids, and how the diarrhoea is affecting their daily life.
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