See also

Dehydration
Gastroenteritis

Key points

1. Bilious (green) vomiting is due to a gastrointestinal obstruction until proven otherwise, and requires urgent surgical referral
2. In a vomiting child without diarrhoea, always consider causes other than gastroenteritis
3. Intracranial causes, including raised intracranial pressure (ICP) and inflicted injury, should always be considered
4. Ondansetron can be used for symptomatic relief; however, cessation of vomiting does not exclude a serious cause

Background 

• Vomiting is a common and non-specific symptom, not a diagnosis
• Infection is the most common cause of acute vomiting
• Bilious vomiting occurs when there is a gastrointestinal obstruction. Bile is dark green rather than yellow. Using a visual aid to clarify vomitus colour with families is helpful
• Early morning vomiting and headache may be due to raised ICP

Bilious vomitus

Differential diagnoses by age

Assessment

History

Symptoms and signs associated with possible diagnoses (table below is not an exhaustive list and presentations can overlap)

Examination

Abdominal

• Abdominal distension could suggest acute abdomen or bowel obstruction (ask parent if abdomen changed in appearance)
• Tenderness
• 'Tinkling' high-pitched or absent of bowel sounds may suggest gastrointestinal obstruction
• Examine testes for torsion, particularly in adolescent boys

Neurological

• Altered conscious state and/or abnormal neurology (eg Cushing's triad) may suggest intracranial pathology
• Bulging fontanelle may be a sign of raised ICP

Assess hydration

• See Dehydration

Red flags

• Bilious vomiting
• Lethargy or listlessness
• Inconsolable +/- bulging fontanelle in infant
• Neck stiffness, photophobia and fever in older child
• Signs of peritonitis
• Persistent vomiting with poor growth or abnormal development

Management

Investigations

• Consider BGL and ketones if BGL <3 mmol/L or >11 mmol/L. Ketotic hypoglycaemia can be a consequence of vomiting, more commonly in younger children
• Most well children with isolated vomiting do not require any other investigations. If you are unsure consult with a senior clinician
• Targeted investigation is directed by likely differential diagnoses

Treatment

• Treat shock with a bolus of 10-20 mL/kg sodium chloride 0.9%
• If BGL <2.6 mmol/L, treat as per hypoglycaemia
• If ketones present, consider carbohydrate source to correct (eg apple juice)
• Consult local surgical team if there is evidence of a surgical cause of vomiting eg bowel obstruction, testicular or ovarian torsion and appendicitis
• Definitive management of a vomiting child is based on cause, see table above

Antiemetics

Ondansetron

• To assist with maintaining hydration in children >6 months of age
• Suggested initial dosage:

• Can be given with vomiting due to head injury provided other signs such as conscious state are carefully monitored
• Cessation of vomiting does not exclude serious causes of vomiting 
• If ondansetron is ineffective, consult senior advice before prescribing other anti-emetics due to side effects

Hydration

• Encourage oral fluids as a first line option eg oral rehydration solution or diluted apple juice (1:1 apple juice to water)
• See Nasogastric fluids for children in which additional enteral fluids are required
• See Intravenous fluids for children not tolerating adequate enteral fluids

Consider consultation with local paediatric team when

• Advice regarding escalation of care
• Patient is acutely unwell and not responding to fluid resuscitation
• Severe metabolic derangement
• Diagnostic uncertainty

Consider transfer when

Child requiring care beyond comfort level of the local hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Consider discharge when

• Alert and able to tolerate small amounts of oral intake
• Normal vital signs
• The cause of vomiting has been identified and adequately managed
  or
• High risk diagnoses have been considered and there is an adequate follow up plan in place with clear instructions on when to seek earlier review

Parent information

Diarrhoea in children 

Vomiting 

Reflux and GORD 

Nausea

Last updated September 2025