Diarrhoea

Diarrhoea

Diarrhoea	If severe dehydration requiring fluid replacement is present: electrolytes, urea.
Acute Infection	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.
Viral	Faeces - microscopy, culture and antigen detection , if indicated.
Bacterial	Faeces - microscopy, culture and antigen detection , if indicated. Blood culture , if indicated.
Protozoal	Faeces - ova, cysts and parasites . If endoscopy is indicated: biopsy of involved bowel. See also Giardiasis , Amoebiasis .
Antibiotic-associated eg	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. Infection with Candida sp is not a cause of antibiotic associated diarrhoea.
Pseudomembranous colitis
Food poisoning
Chronic
Infection
Bacterial	Faeces - microscopy, culture and antigen detection .
Protozoal eg	Faeces - ova, cysts and parasites on 3 occasions (preferably recently collected, warm). If endoscopy is indicated: biopsy of involved bowel.
Giardiasis
Amoebiasis
Ulcerative colitis
Crohns disease
Ischaemic colitis
Radiation proctitis
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
Secondary infection	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.
HIV wasting syndrome
Hyperthyroidism
Irritable bowel
Autonomic neuropathy esp
Diabetes mellitus
Lymphocytic colitis	Colorectal biopsy ; electrolytes -faeces.
Islet cell (non-beta) tumour	Electrolytes - faeces. Gastrointestinal hormones (eg vasoactive intestinal polypeptide) - consult pathologist. See also Pancreatic neoplasm .
Drugs esp	Assay of possible drugs in urine; consult pathologist.
Laxative abuse	Laxatives - urine; magnesium faeces .
Colchicine
Graft versus host disease
Food intolerance/allergy	Rarely a cause of chronic diarrhoea.
Bloody	Faeces microscopy, culture and antigen detection.
Infection eg
Campylobacter jejuni
Enterohaemorrhagic E. coli
Shigella sp
Entamoeba histolytica	See Amoebiasis .
Ulcerative colitis
Crohns disease
Ischaemic colitis
Neoplasia	Lesion biopsy at endoscopy.
Polyps
Colorectal carcinoma	Carcinoembryonic antigen for monitoring course.