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
The terminology for acute infective diarrhoea can be confusing. A simple classification is:
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:
A summary of the diagnostic strategy model is presented in Table 44.1.
Diarrhoea: diagnostic strategy model
|Favorite Table|Download (.pdf) Table 44.1
Diarrhoea: diagnostic strategy model
|Q. ||Probability diagnosis |
|A. ||Acute: |
• Gastroenteritis/infective enteritis
• Dietary indiscretion
• Antibiotic reaction
| ||Chronic: |
• Irritable bowel syndrome
• Drug reactions (e.g. laxatives)
• Chronic infections
|Q. ||Serious disorders not to be missed |
|A. ||Neoplasia: |
• colorectal cancer
• ovarian cancer
• peritoneal cancer
| ||HIV infection (AIDS) |
| ||Infections: |
• enterohaemorrhagic E. coli enteritis
| ||Inflammatory bowel disease: |
• Crohn/ulcerative colitis
• pseudomembranous colitis
| ||Non-microbial food poisoning e.g. death cap mushroom |
| ||Intussusception |
| ||Pelvic appendicitis/pelvic abscess |
|Q. ||Pitfalls |
|A. ||Coeliac disease |
| ||Faecal impaction with spurious diarrhoea |
| ||Lactase deficiency |
| ||Giardia lamblia infection |
| ||Cryptosporidium infection |
| ||Cytomegalovirus in immunocompromised |
| ||Malabsorption states (e.g. coeliac disease) |
| ||Vitamin C and other oral ...|
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