Diarrhoea

Keywords: Traveller's diarrhoea

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

Faeces MCS and antigen, if indicated. Multilex PCR testing if available.

Blood culture, if indicated.

Ova cysts parasites faeces.

  • Protozoal

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 MCS and antigen and/or Clostridium difficile toxin detection.

If endoscopy is indicated, biopsy of involved bowel.

Food poisoning

 

Chronic

 

Infection

  • Viral
  • Bacterial
  • Protozoal

Inflammatory

  • Ulcerative colitis
  • Crohn’s disease
  • Ischaemic colitis
  • Radiation proctitis
  • Lymphocytic colitis

Eg Norovirus, Adenovirus, Rotavirus, CMV if immunocompromised.

Faeces MCS and antigen.

Ova cysts parasites faeces.

If endoscopy is indicated: biopsy of involved bowel.

See also Giardiasis, Amoebiasis.

 

Colorectal biopsy. Electrolytes faeces.

Disaccharide intolerance

Reducing substances faeces and pH faeces.

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

Ova cysts parasites faeces, Faeces MCS and antigen, Mycobacteria testing.

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

Irritable bowel

 

Hyperthyroidism

 

Autonomic neuropathy, especially

  • Diabetes mellitus

 

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

Biopsy

Food intolerance/allergy

Rarely a cause of chronic diarrhoea.

Bloody

MCS faeces / Multiplex PCR.

Infection, especially

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

Inflammatory

  • Ulcerative colitis
  • Crohn’s disease
  • Ischaemic colitis

See Amoebiasis

Neoplasia, including

  • Polyps
  • Colorectal carcinoma

Lesion biopsy at endoscopy.

Carcinoembryonic Ag for monitoring course.

See also Colorectal tumour.