Diarrhoea in Children

Differential Diagnosis

Common Diagnoses

  • Gastroenteritis
  • Other Systemic Infection (e.g. UTI, Otitis Media, Pneumonia)
  • Toddler’s Diarrhoea
  • Medication Side Effects (Usually Antibiotics)
  • Cow’s Milk Protein Allergy (CMPA)

Occasional Diagnoses

  • Lactose Intolerance (Typically Following a Bout of Gastroenteritis in Babies)
  • Faecal Impaction (Causing Overflow Diarrhoea)
  • Irritable Bowel Syndrome
  • Coeliac Disease
  • Other Gastrointestinal Infections, e.g. Giardia

Rare Diagnoses

Ready Reckoner

Key distinguishing features of the most common diagnoses

GastroenteritisOther Systemic InfectionToddler’s DiarrhoeaMedication Side EffectsCMPA
Blood in DiarrhoeaPossibleNoNoNoPossible
Recent or Current AntibioticsNoPossibleNoYesNo
Lasts More than 2 WeeksPossibleNoYesPossibleYes
Other Localising Symptoms (e.g. Respiratory, Urinary or Ear)NoYesNoPossibleNo

Possible Investigations


Possible:Stool culture, urinalysis, MSU, FBC, CRP, ESR, anti-endomysial and anti-gliadin antibodies, faecal calprotectin.

Small Print:Hospital-based tests (e.g. for cystic fibrosis, IBD and to confirm coeliac disease).

  • Stool culture: For microbiological examination if the diarrhoea persists more than a week, is bloody or there is relevant recent foreign travel; send three specimens for ova, cysts and parasites if giardia suspected.
  • Urinalysis: May help if a UTI is suspected as the underlying cause.
  • MSU: For confirmation of a suspected UTI.
  • FBC, ESR, CRP: Hb may be reduced, and CRP/ESR raised in IBD.
  • Anti-endomysial and anti-gliadin antibodies: If coeliac is a possibility.
  • Faecal calprotectin: To help rule out IBD if diarrhoea is prolonged.
  • Hospital-based tests: These might include endoscopy and biopsy in suspected IBD or coeliac disease, and tests for possible cystic fibrosis.

Top Tips

  • It is not unusual for the diarrhoea in gastroenteritis to take a couple of weeks to settle; consider a stool specimen if it is not starting to improve after a week.
  • Don’t overlook faecal impaction as a cause of overflow diarrhoea in children, the clues being soiling and a preceding history of constipation.
  • Lactose intolerance tends to be over-diagnosed and often confused with CMPA. The former is less common, typically follows gastroenteritis and is usually short lived.
  • Undigested food (‘peas and carrots syndrome’) in the persistent loose stool of an otherwise well and thriving child is virtually pathognomic of the harmless toddler’s diarrhoea.

Red Flags

  • In the acute case – particularly in younger children with severe diarrhoea and associated vomiting – assess for dehydration as a priority. If the child is significantly dehydrated, then admission will be needed regardless of cause.
  • Bloody diarrhoea raises the stakes somewhat. In the acute situation, this could be one of the more severe forms of gastroenteritis or, especially in those under 1 year of age, intussusception. In more prolonged cases, it might indicate CMPA or IBD.
  • Very minor, transient weight loss is common during a bout of gastroenteritis. More prolonged weight loss with persistent diarrhoea should, on the other hand, prompt urgent referral.
  • Remember that appendicitis can cause diarrhoea. In such cases, the abdominal pain is usually more marked and constant than in a typical gastroenteritis, where it is typically mild (and therefore not the presenting complaint) and intermittent.
Report errors, or incorrect content by clicking here.