Diarrhoea

Last updated: Saturday, 27, November, 2010
Causes Appropriate Tests
If severe dehydration requiring fluid replacement is present: electrolytes, urea.
Acute

Testing is only indicated when diarrhoea is severe or persistent, or if the patient requires hospitalisation.

Testing may also be appropriate when an epidemic is suspected.

The selection of tests should take recent travel into account - consult pathologist.

Infection

  • Viral
  • Bacterial
  • Protozoal

 

Faeces - microscopy, culture and antigen detection, if indicated.

Blood culture, if indicated.

Faeces - ova, cysts and parasites.

If endoscopy is indicated: biopsy of involved bowel. See also Giardiasis, Amoebiasis

Antibiotic-associated

  • Pseudomembranous colitis

Diarrhoea of varying severity is a common adverse effect of antibiotics.

If severe and/or persistent: faeces - microscopy, culture and antigen detection and/or Clostridium difficile toxin.

If endoscopy is indicated: biopsy of involved bowel.

Food poisoning
Chronic

Infection

  • Bacterial
  • Protozoal

Inflammatory

Faeces - microscopy, culture and antigen detection.

Faeces - ova, cysts and parasites.

If endoscopy is indicated: biopsy of involved bowel.

See also Giardiasis, Amoebiasis

 

 

Colorectal biopsy; electrolytes -faeces.

Disaccharide intolerance

Faeces - reducing substances and pH.

Small bowel biopsy with measurement of disaccharidases.

Sugar tolerance tests, with assay of breath hydrogen or plasma glucose, are less frequently used.

Malabsorption

HIV infection

 See HIV infection and AIDS
  • Secondary infection
  • HIV wasting syndrome

Faeces - ova, cysts and parasites; faeces - microscopy, culture and antigen detection, mycobacteria testing.

Biopsy of bowel for evidence of CMV, protozoal or mycobacterial infection, if indicated.

Irritable bowel

Hyperthyroidism

Autonomic neuropathy, especially 

Islet cell (non-beta) tumour

Electrolytes - faeces. Gastrointestinal hormones (eg, vasoactive intestinal polypeptide) - consult pathologist.

See also Pancreatic neoplasm.

Drugs, especially 

  • Laxative abuse
  • Colchicine

Assay of possible drugs in urine; consult pathologist.

Laxatives - urine; magnesium faeces.

Graft versus host disease

Food intolerance/allergy

 Rarely a cause of chronic diarrhoea.
Bloody Faeces microscopy, culture and antigen detection.

Infection, especially

  • Campylobacter jejuni
  • Enterohaemorrhagic Escherichia coli
  • Shigella spp
  • Entamoeba histolytica

Inflammatory

 

See Amoebiasis

Neoplasia, including

  • Polyps
  • Colorectal carcinoma

Lesion biopsy at endoscopy.

Carcinoembryonic antigen for monitoring course.

See also carcinoma -Colonic carcinoma