Acute gastroenteritis and oral rehydration — Rapid

Synopsis

Recognise dehydration and serious alternatives in a vomiting or diarrhoeal child, then restore fluid safely with age-appropriate oral rehydration while limiting unnecessary tests, antibiotics and dietary restriction.

Assess hydration from appearance, responsiveness, urine, eyes, mucosa, heart rate, breathing, pulses, capillary refill, skin and peripheral temperature; no single sign is sufficient.
First-line treatment for clinical dehydration without shock is low-osmolarity ORS: give 50 ml/kg over 4 hours in addition to maintenance, frequently in small amounts.
Continue breastfeeding throughout; if vomiting persists, try 5 ml ORS every 1 to 2 minutes and consider nasogastric delivery before intravenous fluid when safe.
During rehydration, consider 5 ml/kg ORS after each large watery stool for children at increased risk of recurrent dehydration.
Shock needs urgent isotonic intravenous fluid under a paediatric resuscitation protocol; reassess after every bolus and reconsider sepsis or haemorrhage if response is poor.
After rehydration, restart full-strength milk and usual age-appropriate food; avoid fruit juice and fizzy drinks until diarrhoea has stopped.
Do not routinely use antibiotics, antidiarrhoeal medicines, probiotics or routine stool tests; select treatment and testing from pathogen risk and severity.
Give families explicit return advice and infection-control guidance, including exclusion from school or childcare until at least 48 hours after the last diarrhoea or vomiting episode.

Key red flags

Bilious green vomit, abdominal distension, focal guarding or bloody stool with severe pain suggests obstruction, volvulus, intussusception or surgical inflammation.

Lethargy, altered responsiveness, sunken eyes, weak pulses, prolonged capillary refill, cold mottled limbs or reduced urine indicates important dehydration or shock.

Infants under 6 months, low-birth-weight children and those with malnutrition, immunodeficiency or major comorbidity can deteriorate quickly.

More than five diarrhoeal stools or more than two vomits in 24 hours, inability to keep fluids down or stopping breastfeeding increases dehydration risk.

Non-blanching rash, neck stiffness, bulging fontanelle, respiratory distress or toxic appearance suggests sepsis or another systemic diagnosis.

Blood or mucus in stool, recent foreign travel, persistent diarrhoea beyond day 7 or diagnostic uncertainty supports microbiological investigation.

Investigation priorities

First-line clinical hydration assessmentFirst stepFirst line

Classify severity and choose home, oral, nasogastric or intravenous management.

Management branches

No dehydrationSupport safe home intake

The child is clinically hydrated and has no surgical or systemic red flag.

Continue breast or usual milk feeds and offer ORS after losses in higher-risk children.
Avoid juice and fizzy drinks and restart ordinary food as appetite permits.
Provide infection-control and explicit urine, behaviour, vomiting and pain return criteria.

Key medicines

Low-osmolarity oral rehydration solutionFor a child with clinical dehydration, give 50 ml/kg enterally over 4 hours in addition to maintenance, frequently in small amounts; consider 5 ml/kg after each large watery stool in higher-risk children.Mix with the exact stated water volume and do not add sugar or salt; use specialist monitoring for hypernatraemia and stop enteral therapy if bilious vomiting or obstruction is suspected.

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