Acute Gastroenteritis (Medical students)
Definition of Acute Gastroenteritis (AGE) in Children
Acute gastroenteritis is defined as a decrease in stool consistency (loose or liquid) and/or an increase in the frequency of evacuations (typically more than three in 24 hours), with or without associated fever and vomiting. Diarrhoea usually lasts less than 7 days and not more than 14 days.
Epidemiology
Viral agents are the most common cause of AGE in children, especially rotavirus, for which an oral vaccine is available and given in two doses during the first 6 months of life. Other viral causes include adenovirus, norovirus, and astrovirus. Viral infections often present with vomiting and upper respiratory symptoms.
Bacterial agents such as Campylobacter and Salmonella are less common but more likely to cause severe symptoms. Indicators of bacterial gastroenteritis include high fever, bloody stools, abdominal pain, and signs of systemic involvement (e.g. irritability, lethargy, seizures).
Incidence: 0.5–2 episodes per child per year in children under 3 years. Breastfeeding is protective, while daycare attendance is associated with higher infection rates.
Assessment
- Exclusion of other significant causes of vomiting and diarrhoea (differential diagnosis).
- Evaluation and treatment of dehydration.
Risk Factors for Dehydration
- Infants <6 months of ag
- Prematurity
- Malnutrition
- 6 diarrhoeal stools in 24 hours
- 3 vomiting episodes in 24 hours
- Inability to tolerate oral fluids
Assessment of Dehydration
- General appearance and consciousness
- Hydration status: skin turgor, eyes, tears, oral mucosa, fontanelles
- Cardiorespiratory: skin colour, perfusion, extremity temperature, heart rate, BP, respiratory rate
- Urine output
Classification:
- No/minimal dehydration: Child is alert, well-appearing, moist mucosa, normal skin turgor and perfusion, normal urine output.
- Clinical dehydration: Child appears unwell, irritable or lethargic, dry mouth, sunken eyes, decreased turgor, tachycardia/tachypnoea, reduced urine output.
- Circulatory shock: Decreased consciousness, cold extremities, mottled skin, prolonged CRT, weak pulses, hypotension, anuria.
Differential Diagnosis
- Sepsis: Urinary tract infection, otitis media, meningitis, pneumonia
- Acute surgical abdomen: Appendicitis, intussusception, bowel obstruction
- Metabolic: Diabetic ketoacidosis
⚠️ Avoid attributing fever and vomiting in infants solely to AGE — these may indicate serious infections like meningitis or UTI.
Indications for Hospitalisation
- Severe dehydration or shock
- Suspected surgical cause
- High risk of dehydration (age, frequent vomiting/diarrhoea, poor oral intake)
- Underlying chronic conditions (e.g., diabetes, renal failure)
- Inadequate home care or caregiver support
Investigations
Stool culture: Not routinely required. Indicated when:
- Before starting antibiotics
- Immunocompromised patient
- Part of an outbreak investigation
Blood tests: Urea, creatinine, electrolytes, venous blood gases in children needing IV fluids. A normal serum bicarbonate level reduces the likelihood of significant dehydration.
Rehydration
- Oral rehydration solution (ORS) is the first-line therapy, leveraging glucose-facilitated sodium absorption.
- If oral rehydration is not tolerated, enteral (NG) rehydration is preferred over IV when feasible.
- Enteral methods are associated with fewer complications and are effective in most cases.
Nutritional Management
- Reintroduce feeding within 4–6 hours of starting rehydration.
- Continue breastfeeding throughout the illness.
- No need to dilute formula or switch to lactose-free preparations in most cases.
- Avoid fruit juices and fizzy drinks.
Pharmacological Therapy
Anti-emetics are not routinely recommended but may be considered (e.g., ondansetron) in specific cases to reduce vomiting and facilitate ORS intake.
Loperamide and other anti-diarrhoeals are contraindicated in young children.
Probiotics such as Lactobacillus and Saccharomyces boulardii may reduce duration of diarrhoea.
Antibiotics are usually unnecessary but indicated in:
- Severe or invasive bacterial infections (bloody stools, high fever)
- Shigella (proven or suspected)
- Salmonella in high-risk patients (infants <3 months, immunocompromised)
- Campylobacter, if dysenteric
- ETEC (e.g., traveller’s diarrhoea)
- Clostridium difficile (moderate to severe cases)
Hospital Management
- IV access: Send for renal profile and blood gases
- Treat shock with normal saline boluses (20 ml/kg)
- IV fluids: Usually 5% Dextrose in 0.45% Normal Saline ± potassium (if not hyperkalaemic and once urine is passed). Hourly rate = (maintenance + deficit)/24 hours
Monitor clinical status and urine output.
Correct hypernatraemic dehydration slowly to avoid cerebral oedema and seizures
Gradually reintroduce oral fluids and normal feeding.
Home Management
- Oral rehydration with ORS, followed quickly by appropriate nutrition (breast/formula milk, solids)
- Avoid fruit juices and carbonated drinks
- Use barrier creams to protect skin from nappy rash
Seek medical attention if:
- Persistent vomiting or diarrhoea (10 times in 24 hours)
- The child is not drinking or retaining fluids
- No urine output for 8 hours
- Increasing lethargy or dry mouth
- Parental concern or inability to cope
CASE HISTORIES
Case 1
8 month old infant brought to A&E on Saturday evening. His young mother requested admission because the child passed diarrhoea on three occasions. On clinical examination, the child looks well, alert and hydrated.
Do you think that this child requires admission?
Case 2
A 6 month old baby girl is brought to casualty. She had been seen 12 hours before for vomiting and diarrhoea, and treated at home with ORS and milk feeds. Her parents were anxious because she continued to pass diarrhoea and cried intermittently. Clinical examination shows an alert and well-hydrated child, the abdominal examination is normal.
How will you manage this case?
Case 3
2 month old baby boy presented with fever 38.2°C, crying and vomiting on 2 occasions. On clinical examination he was well hydrated, febrile, irritable. No signs of meningism. The abdomen is soft and slightly distended.
What is the diagnosis? What is your management?
Case 4
8 month old infant brought to casualty for spasmodic pain associated with pallor and irritability. He was afebrile and vomited twice.
What other questions would you ask the parents? Likely diagnosis? Any investigations?
Case 5
2 year old child presented with acute onset of vomiting, followed by watery diarrhoea. He complained of intermittent abdominal pain. He had low-grade fever, coryza, cough and nasal congestion. On examination he was well and alert and no signs of dehydration.
What is the likely diagnosis? How would you treat?
Case 6
A 3 year old girl presented acutely with nausea, vomiting and abdominal pain. She had been eating and drinking more than usual in the past two weeks. On examination she was severely dehydrated and tachypnoeic.
What immediate investigations would you perform?
Case 7
A 2 year old child was successfully treated for gastroenteritis with ORS. However on the re-introduction of a normal diet she again developed watery diarrhoea and perineal excoriations.
What is the likely cause? Treatment?
8 month old infant brought to A&E on Saturday evening. His young mother requested admission because the child passed diarrhoea on three occasions. On clinical examination, the child looks well, alert and hydrated.
Do you think that this child requires admission?
Case 2
A 6 month old baby girl is brought to casualty. She had been seen 12 hours before for vomiting and diarrhoea, and treated at home with ORS and milk feeds. Her parents were anxious because she continued to pass diarrhoea and cried intermittently. Clinical examination shows an alert and well-hydrated child, the abdominal examination is normal.
How will you manage this case?
Case 3
2 month old baby boy presented with fever 38.2°C, crying and vomiting on 2 occasions. On clinical examination he was well hydrated, febrile, irritable. No signs of meningism. The abdomen is soft and slightly distended.
What is the diagnosis? What is your management?
Case 4
8 month old infant brought to casualty for spasmodic pain associated with pallor and irritability. He was afebrile and vomited twice.
What other questions would you ask the parents? Likely diagnosis? Any investigations?
Case 5
2 year old child presented with acute onset of vomiting, followed by watery diarrhoea. He complained of intermittent abdominal pain. He had low-grade fever, coryza, cough and nasal congestion. On examination he was well and alert and no signs of dehydration.
What is the likely diagnosis? How would you treat?
Case 6
A 3 year old girl presented acutely with nausea, vomiting and abdominal pain. She had been eating and drinking more than usual in the past two weeks. On examination she was severely dehydrated and tachypnoeic.
What immediate investigations would you perform?
Case 7
A 2 year old child was successfully treated for gastroenteritis with ORS. However on the re-introduction of a normal diet she again developed watery diarrhoea and perineal excoriations.
What is the likely cause? Treatment?