These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline. 

Read the full PCH Emergency Department disclaimer.


To guide staff with the assessment and management of gastroenteritis.


Gastroenteritis is vomiting, diarrhoea or both caused by viruses (in 70% of cases), bacteria (20%) and protozoa (10%).
  • Vomiting may occur before the onset of diarrhoea. However, vomiting in isolation may be due to a wide range of other potentially serious conditions.
  • Concerning features suggesting an alternate diagnosis are significant abdominal pain, co-morbidities, < 6 months age, high fever, prolonged symptoms, or signs suggesting a surgical cause.
  • In infants, vomiting must be distinguished from the normal phenomenon of regurgitation.
  • Oral / NGT rehydration is preferable to intravenous except in severe cases.

Gastroenteritis management flowchart. Click to enlarge.

Risk factors for developing gastroenteritis

  • Attending childcare
  • Recent travel overseas
  • Evaluation of the severity of dehydration is difficult even by a senior doctor
  • Non-dehydrated patients do not need a fluid trial in the ED.



No or mild dehydration  <3% weight loss  No physical signs or thirst, dry mucus membranes, reduced urine output 
Moderate dehydration  3-6% weight loss  Dry mucus membranes, reduced urine output, tachycardia, sunken eyes, minimal or no tears, diminished skin turgor, altered neurological status (drowsiness, irritability).
Severe dehydration  7-12% weight loss  Increasingly marked signs from the above group, plus: decreased peripheral perfusion, (cool, mottled, pale peripheries, capillary refill time >2 seconds), anuria, hypotension, circulatory collapse. 


  • No investigations are required in mild cases of gastroenteritis
  • Stool specimen is required for patients with bloody stool, prolonged diarrhoea and recent travel overseas
  • FBC, U&E and VBG should be done if inserting an intravenous cannula to commence intravenous fluids

Differential diagnoses


  • Non-dehydrated children can be discharged after reassurance, education and a health fact sheet to go home.
  • Non-dehydrated children can eat as tolerated, but should avoid sweet and fatty foods.
  • Continue breastfeeding but add extra fluids as required.
  • Ondansetron may be used in the Emergency Department before a fluid trial but not as a discharge medication. It can make the diarrhoea last longer.
  • In moderately dehydrated children oral / nasogastric rehydration is preferable to intravenous as it corrects acidosis quicker, the diarrhoea and vomiting settle faster and appetite returns sooner.
  • Severe dehydration needs admission for intravenous rehydration and electrolytes need to be checked.

Further management

Mild dehydration  Oral fluids: 1mL/kg every 10 minutes of oral rehydration solution or water (if dislikes ORS) or watered down apple juice can be provided whist awaiting medical assessment.
Fluids high in sugar (cola, apple juice, sports drinks, containing ≤  20 mmol/L sodium with osmolality 350-750 mOsm/L) should be avoided.
Solids and milk can be continues if the child is interested and not dehydrated.
Most mildly dehydrated children can be discharged.
On discharge: ensure the caregiver is discharged with appropriate education on gastroenteritis, including how to provide fluid and signs of dehydration.
Moderate dehydration  Consider Ondansetron (0.1-0.2mg/kg oral or IV).
Oral fluid trial of 1mL/kg every 10 minutes of oral rehydration solution for 1-2 hours.
Fluids high in sugar (cola, apple juice, sports drinks, containing  ≤ 20 mmol/L sodium with osmolality 350-750 mOsm/L) should be avoided.
Solids and milk can be continues if the child is interested and not dehydrated otherwise wait until rehydrated. 
Severe dehydration  Insert IV cannula, check FBC. U&E, and VBG.
IV fluid bolus: 20mL/kg bolus of 0.9% saline (repeat if required) and admit under the General Paediatric team.
Investigate possible underlying causes.
Continue IV fluids: 0.9% saline + 5% glucose (maintenance + deficit over 24 hours)
If hypernatraemia (Na>150mmol/L) IV fluids are to be given over 48-72 hours.

If the child fails oral fluid trial:

  • Nasogastric tube (NGT) rapid rehydration: 50mL/kg over 4 hours with oral rehydration solution (ORS). This corrects for 5% dehydration.
  • Admit to the Emergency Department Short Stay Ward 
  • If the child vomits reduce the rapid rehydration rate to 50mL/kg over 6 hours.
If the child fails NGT rapid rehydration (> 2 vomits):
  • Admit to General Paediatric team.
  • Hourly observations (at least) HR, RR, temperature, BP, Capillary refill time.
  • Option 1: NGT fluid (maintenance + deficit).
  • Option 2:  IV fluids 0.9% saline + 5% dextrose (maintenance + deficit).

Use the following paediatric fluid rate calculator:

Fluid calculation
1. Deficit volume
Deficit volume = weight (kg) x % dehydration x 10mL
2. Maintenance
<10kg = 100mL/kg/24 hours
10-20kg - 1000mL + (50mL for each kg over 10kg) / 24 hours
>20kg = 1500mL + (20mL for each kg over 20kg) / 24 hours
3. Hourly rate
Hourly rate = (deficit volume + 24 hours maintenance fluids) divided by 24 


  • Ondansetron can be used before a fluid trial or if the child vomits during rapid rehydration. It is not recommended as a discharge medication.
  • No other anti-emetics or anti-diarrhoeal agents are to be used in infants or children with suspected gastroenteritis.

Admission criteria

  • Failed rapid rehydration with nasogastric tube (NGT)
  • Severe dehydration requiring intravenous fluids.

Referrals and follow-up

  • Mild dehydration who are sent home after oral fluid trial should have a GP review at 24 hours.


  • Ensure all children are weighed (bare weight < 12 months old, light clothing for all other children)
  • Ensure the child is reweighed prior to discharge
  • Utilise the appropriate rehydration form if the child is having a trial of fluids.


  • Baseline observations include HR, RR, temperature, BP and capillary refill
  • Minimum of hourly observations should be recorded whilst in the Emergency Department
  • Any significant changes should be reported immediately to the medical team
  • Fluid input/output is to be monitored and documented.


  1. NICE Guidelines UK Diarrhoea and vomiting in children under 5 (CG84) 2011
  2. Practice parameter: the management of acute gastroenteritis in young children. American Academy of Pediatrics, Provisional Committee on Quality Improvement, Subcommittee on Acute Gastroenteritis. Paediatrics 1996;97424-35
  3. European Society for Paediatric Gastroenterology, Hepatology, and Nutrition/European Society for Paediatric Infectious Diseases
  4. Evidence-based Guidelines for the Management of Acute Gastroenteritis in Children in Europe
  5. Journal of Pediatric Gastroenterology and Nutrition 46:  S181-S184  2008

Endorsed by:  Executive Director, Medical Services  Date:  Oct 2021

 Review date:   Oct 2022

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