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A dirty cook gives diarrhoea quicker than rhubarb.

Tung-su Pai (time uncertain)


Diarrhoea is defined as an intestinal disorder characterised by abnormal frequency and liquidity of faecal evacuations.


Acute self-limiting diarrhoea, which is very common and frequently not seen by the medical practitioner, is usually infective and mild, and resolves within days. In Australia most infective cases are viral. The causes of diarrhoea are numerous, thus making a detailed history and examination very important in leading to the diagnosis. ‘Chronic’ diarrhoea is that lasting at least 4–6 weeks. Important causes are presented in FIGURE 44.1.


Important causes of chronic diarrhoea

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The terminology for acute infective diarrhoea can be confusing. A simple classification is:


  • vomiting and diarrhoea = gastroenteritis

  • diarrhoea (only) = enteritis


Key facts and checkpoints

  • The characteristics of the stool provide a useful guide to the site of the bowel disorder.

  • Disorders of the upper GIT tend to produce diarrhoea stools that are copious, watery or fatty, pale yellow or green.

  • Colonic disorder tends to produce stools that are small, of variable consistency, brown and may contain blood or mucus.

  • Acute gastroenteritis should be regarded as a diagnosis of exclusion.

  • Chronic diarrhoea is more likely to be due to protozoal infection (e.g. amoebiasis, giardiasis or Cryptosporidium) than bacillary dysentery.

  • A history of travel, especially to countries at risk of endemic bowel infections, is essential.

  • Certain antibiotics can cause an overgrowth of Clostridium difficile, which produces pseudomembranous colitis.

  • Coeliac disease, although a cause of failure to thrive in children, can present at any age.

  • In disorders of the colon the patient experiences frequency and urgency but passes only small amounts of faeces.

  • Diarrhoea can be classified broadly into 4 types:

    • acute watery diarrhoea

    • bloody diarrhoea (acute or chronic)

    • chronic watery diarrhoea

    • steatorrhoea


A diagnostic approach


A summary of the diagnostic strategy model is presented in Table 44.1.

Table Graphic Jump Location
Table 44.1

Diarrhoea: diagnostic strategy model

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