Differentials
Food poisoning
SIGNS / SYMPTOMS
Predominant symptom is vomiting.
It is easy to confuse the symptoms of TD with those of food poisoning; the latter is of much earlier onset and is characterised more by vomiting than by diarrhoea (except that caused by Clostridium perfringens).
Food poisoning, while self-limited, does not respond to antibiotics.
Staphylococcus aureus and Bacillus cereus (both forming heat-stable toxins) or C perfringens (heat-labile toxins) cause most food poisoning cases.
Pre-formed toxins (from S aureus or B cereus) produce symptoms (vomiting > diarrhoea) within 1-6 hours, whereas C perfringens infections, with in vivo toxin formation, cause diarrhoeal symptoms within 8-16 hours. Most TD bacterial infections, on the other hand, become symptomatic 16 hours after ingestion.[20]
INVESTIGATIONS
Typically diagnosed clinically, but bacterial cultures or virological studies may elicit culprit organism.
Irritable bowel syndrome
SIGNS / SYMPTOMS
Diarrhoea or constipation, both associated with abdominal pain. No weight loss, fever, or systemic symptoms. Symptom relief usually occurs after bowel movement. Post-TD irritable bowel syndrome (IBS) is usually of the diarrhoea subtype (IBS-D).[6]
INVESTIGATIONS
Normal examination, and laboratory and bowel work-up.
Secondary disaccharidase (or other dietary) deficiency
SIGNS / SYMPTOMS
Exacerbation of symptoms with dairy products or other food class. Often difficult to solicit. Generally resolves in days to a week.
INVESTIGATIONS
Normal examination and laboratory and bowel work-up
Malabsorptive conditions
SIGNS / SYMPTOMS
Persistent diarrhoea, may be unusually foul smelling or greasy. Can be attributed to small intestinal bacterial overgrowth, or changes in microbiome or in structural absorptive capacity of microvilli.
INVESTIGATIONS
Faecal fat, faecal bile acid, D-xylose, hydrogen/methane breath testing, colonoscopy/endoscopy may be revealing.
Clostridioides difficile colitis
SIGNS / SYMPTOMS
Persisting diarrhoea with fever, abdominal pain/tenderness, and weight loss, often following use of antibiotics (with or without travel history).
INVESTIGATIONS
C difficile stool toxin positive (enzyme immunoassay/polymerase chain reaction tests are available).
Coeliac disease
SIGNS / SYMPTOMS
Persisting diarrhoea with malabsorption (with or without travel history).
May be associated with dermatitis herpetiformis.
INVESTIGATIONS
IgA anti-tissue transglutaminase (anti-tTG) usually positive.
Because IgA deficiency may interfere with coeliac testing, an IgA level should also be obtained.
Crohn's disease
SIGNS / SYMPTOMS
Diarrhoea (with or without travel history), abdominal pain, fever, perianal fistulae.
INVESTIGATIONS
Elevated erythrocyte sedimentation rate, elevated faecal calprotectin, anaemia, haem-positive stools. Colonoscopy differentiates most cases of Crohn's disease from ulcerative colitis. Ulcerative colitis always involves the rectum and is contiguous versus intermittent. Crohn's disease often has perianal involvement, rectal sparing, and a tendency to form fistulae.
Ulcerative colitis
SIGNS / SYMPTOMS
Bloody diarrhoea (with or without travel history), abdominal pain, fever, no perianal disease.
INVESTIGATIONS
Elevated erythrocyte sedimentation rate, elevated faecal calprotectin, anaemia, haem-positive stools. Colonoscopy differentiates most cases of Crohn's disease from ulcerative colitis. Ulcerative colitis always involves the rectum and is contiguous versus intermittent. Terminal ileitis may be present in ulcerative colitis with pancolitis due to backwash.
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