Differential Diagnoses

Bear in mind differentials

By far the most common cause is an infective (usually viral) gastroenteritis.

  • Surgical – e.g. obstruction, intussusception, appendicitis. Ask about pain, distention, bile in vomitus
  • Infection – ?UTI, ?Meningitis. Suspect if high fevers
  • Metabolic Conditions – Diabetes, Haemolytic Uraemic Syndrome. Suspect if Polydipsia, polyuria
  • Injury – in particular head injury with vomiting – raised ICP / headache



Think about fluids in vs fluid out. It is difficult for parents to accurately assess intake. The easiest way to assess this is with the proportion of their norma intake.

  • Ask about proportions
  • <50% of normal fluid intake
  • Wet nappies – >8hrs between wet nappies is a warning sign / at least 3 wet nappies per day is the bare minimum of normal
  • Abnormal losses – >5 episodes of D or V


Degree of dehydration

  • MILD <5%
    • Thirsty
    • Reduced UO
    • Dry mucosa
    • Mild tachycardia
    • TREATMENT – smaller, more frequent feeds (breast / formula / or oral rehydration fluids). If unsuccessful – to ED for rehydration. NG or IV.
  • MODERATE 5-10%
    • As above, plus
    • Lethargy
    • Sunken fontanelle / eyes
    • Reduced skin turgor
  • SEVERE >10%
    • As above, plus
    • Decrease in level of consciousness
    • Signs of shock (hypotension, poor perfusion, cap refil etc)



  • Children with signs of shock need urgent rehydration with IV fluids
  • Otherwise – oral rehydration is usually the preferred method
  • If breast-fed and young (<1 year) then more frequent breast feeds are the preferred method
  • If this is not tolerated, or an older child, then oral rehydration fluids are preferred option. However, these are often not well tolerated. One study has shown that apple juice was as good if not better than oral rehydration fluids – probably because children prefer the taste and so drink more of it! In younger children, diluting the juice may be preferable (e.g. ½ or ¼ strength).
  • Children (and parents) may need a lot of encouragement. Most emergency departments will have a protocol with an oral rehydration chart – and parents will be encouraged to give a set amounts – e.g. 10mls every 10 minutes – via an oral syringe if the child is really struggling



  • Dystonic reactions. Stemetil and metoclopramide are CONTRAINDICATED IN CHILDREN. Most common in children under 2 years. Benztropine is a good anti-dystonic, but can only be used in children over 1 yr. In children <1yr, antihistamines / diazepam should be used
    • Dystonic reactions are most common in children under 2 and rare in children over 11
    • Can be treated with benztropine in children over 1
    • In children under 1 – consider diazepam
  • Ondansetron is suitable, even in mild dehydration – doses recommended by the Royal Children’s Hospital in Melbourne are:
    • Weight 0-8Kgs – DO NOT USE
    • Weight 8-15kgs – 2mg Ondansetron TDS PRN
    • Weight 15-30kgs – 4mg Ondansetron TDS PRN
    • Weight 30+Kgs – 8mg Ondansetron TDS PRN
  • If rehydration still fails – consider NG tube rehydration of IV fluids


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