Diarrhoea
Overview
While diarrhoea is commonly infectious, it can also be caused by malabsorption, drugs and other non-gastrointestinal pathologies.
Aetiology
Causes of Diarrhoea
Inflammatory
- Viral infection - rotavirus, norovirus, adenovirus
- Bacterial infection - Campylobacter, Shigella, Salmonella, Escherichia coli, Clostridium difficile, Vibrio cholerae, Staph aureus
- Parasitic infection - giardiasis
- Inflammation - Crohn's disease, ulcerative colitis, diverticulitis, appendicitis, ischaemic colitis, radiation colitis, colorectal cancer
Fatty
- Malabsorption - lactose / fructose intolerance, coeliac disease, mesenteric ischaemia, short bowel syndrome, amyloidosis, tropical sprue, Whipple disease
- Exocrine deficiency - cholestasis, pancreatic exocrine insufficiency
Watery
- Medications - laxatives, magnesium, antihypertensives, lipid-lowering meds, PPIs, NSAIDs, antibiotics, certain chemotherapy
- Endocrine - hyperthyroidism, adrenocortical insufficiency
- Neuroendocrine tumour - gastrinoma, VIPoma, carcinoid syndrome
- GI neoplasia - colorectal cancer, lymphoma, villous adenoma
- Alcohol abuse
Functional
- Irritable bowel syndrome
Don't forget to check whether your patient is on laxatives, as this may be a simply treated cause for their diarrhoea.
History of Presenting Complaint
Stools
The frequency, colour and consistency of the patient's stools.- Watery stoolsSuggestive of osmotic or secretory cause
- Steatorrhoea: fatty stools that floatSuggestive of malabsorption or exocrine deficiency
- Blood-stained stoolsSuggestive of inflammatory cause, e.g. infection, inflammation, ischaemia or tumour
- High-volume diarrhoeaSuggestive of small bowel pathology
- Increased frequency of small volume diarrhoeaSuggestive of large bowel pathology
- Alternating diarrhoea and constipationSuggestive of irritable bowel syndrome (IBS)
Triggers
Whether there was any inciting event prior to onset of the diarrhoea.- Post recent tavelSuggestive of infection, especially enterotoxic E coli
- After eating seafoodSuggestive of Vibrio infection
- During or after a course of antibioticsPotential Clostridium difficile infection
Associated Symptoms
Whether the diarrhoea is associated with any other symptoms.- Nausea / vomitingSuggestive of inflammatory cause, particularly infection
- Severe abdominal painSuggestive of inflammatory cause
- FeversSuggestive of infectious cause
- Weight lossSuggestive of malabsorption or cancer
- Perianal discharge or fistulaSuggestive of inflammatory bowel disease
Severity
- Whether the patient has been able to keep down any fluids, and how the diarrhoea is affecting their daily life.
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