Gastroenteritis
Exam Tips
- In OSCEs, prioritise dehydration severity and perfusion assessment before labelling the likely pathogen.
- Bloody diarrhoea plus abdominal pain should trigger concern for invasive bacterial disease and STEC; do not reflexively prescribe antibiotics.
- Core management mark points: ORS first-line, continue feeding, avoid anti-diarrhoeals in children, and provide clear safety-net advice.
- Remember UK infection-control advice: child should stay off school/nursery until 48 hours symptom-free.
Definition
Gastroenteritis in children is an acute, usually self-limiting enteric infection causing sudden-onset diarrhoea (typically 3 or more loose stools in 24 hours), with or without vomiting, fever, and abdominal pain. In UK practice it is most often viral, but bacterial and parasitic causes are important when there is blood in stool, severe illness, prolonged symptoms, or relevant exposure history (for example travel, outbreaks, or contaminated food).
Pathophysiology
Pathogens are transmitted mainly by the faeco-oral route (person-to-person, foodborne, waterborne, contaminated surfaces). Viruses such as rotavirus and norovirus commonly infect small-intestinal enterocytes, causing transient villous dysfunction, reduced absorptive capacity, and osmotic diarrhoea; vomiting is driven by gut-brain neurohumoral signalling and gastric dysmotility. Bacterial disease may be toxin-mediated (for example Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, with rapid-onset vomiting/diarrhoea) or invasive/inflammatory (for example Campylobacter, Shigella, Salmonella, STEC), producing mucosal injury, cytokine release, and sometimes bloody stool. The key clinical consequence is fluid and electrolyte loss leading to dehydration, metabolic acidosis, reduced perfusion, and in severe cases hypovolaemic shock.
Risk Factors
- Age under 5 years (especially infants and toddlers)
- Close-contact settings (nurseries, schools, care environments, household outbreaks)
- Recent contact with someone with vomiting/diarrhoea
- Poor hand hygiene or contaminated fomites/surfaces
- High-risk food or water exposure (undercooked poultry, unpasteurised milk, reheated rice/meat dishes, untreated water)
- Recent foreign travel (traveller's diarrhoea risk varies by destination and duration)
- Immunocompromise or significant comorbidity
- Recent antibiotic exposure (raises risk of Clostridioides difficile-associated diarrhoea)
Clinical Features
Symptoms
- Acute watery diarrhoea
- Vomiting (often prominent and abrupt in norovirus)
- Abdominal cramps/pain
- Fever
- Nausea, reduced oral intake
- Blood or mucus in stool suggests invasive bacterial infection/dysentery
- Lethargy, irritability, thirst, reduced urine output suggest dehydration
Signs
- Tachycardia
- Dry mucous membranes and reduced tears
- Sunken eyes or depressed fontanelle (infants)
- Prolonged capillary refill time and cool peripheries in severe dehydration
- Reduced skin turgor
- Tachypnoea (can reflect metabolic acidosis)
- Weight loss compared with baseline
- Altered consciousness or hypotension in impending/established shock
Investigations
Management
Lifestyle Modifications
- Use oral rehydration solution (ORS) early and continue age-appropriate feeding (including breast milk/formula) once rehydration starts
- For mild-moderate dehydration, give ORS in small frequent volumes; replace ongoing losses after each loose stool/vomit
- Avoid fruit juices, carbonated drinks, and undiluted sugary drinks during rehydration
- Strict hand hygiene and exclusion from school/nursery until 48 hours after last diarrhoea/vomiting episode
- Safety-net: seek urgent care for persistent vomiting, blood in stool, reduced urine, drowsiness, severe abdominal pain, or signs of shock
- See Figure from paediatric dehydration assessment charts in your core textbook (clinical signs by dehydration severity)
Pharmacological Treatment
Oral rehydration therapy
- Oral rehydration salts (for example Dioralyte) 1 sachet dissolved in 200 mL water; typical rehydration target 50 mL/kg over 4 hours for clinical dehydration, then about 10 mL/kg per loose stool
First-line treatment. Give frequent small sips; use nasogastric route if oral intake fails. Do not mix ORS with juice/fizzy drinks.
Analgesic/antipyretic
- Paracetamol 15 mg/kg per dose every 4-6 hours as needed (max 4 doses in 24 hours; usual max 60 mg/kg/day)
Use for fever/discomfort. Avoid NSAIDs such as ibuprofen in dehydrated children because of AKI risk.
IV fluid resuscitation (if shock or failed enteral rehydration)
- Sodium chloride 0.9% IV bolus 20 mL/kg, reassess after each bolus
Use isotonic crystalloid in haemodynamic instability. Escalate senior/paediatric review early and monitor electrolytes closely.
Antimicrobials (targeted, not routine)
- Azithromycin 10 mg/kg once daily for 3 days (max 500 mg/day) in selected severe bacterial/traveller's diarrhoea cases
- Ceftriaxone 50-80 mg/kg IV once daily (max 4 g/day) for severe invasive bacterial infection under specialist care
Most children do not need antibiotics. Choose therapy by organism/susceptibility and severity. Avoid antibiotics in suspected/confirmed STEC because of increased HUS risk.
Complications
- Dehydration with electrolyte disturbance
- Hypovolaemic shock
- Acute kidney injury
- Hypoglycaemia (especially infants)
- Seizures (usually fever/electrolyte related)
- Haemolytic uraemic syndrome (classically after STEC infection)
- Temporary lactose intolerance after mucosal injury
- Malnutrition/weight loss if prolonged illness
- Public health outbreaks in closed settings
Prognosis
Most paediatric gastroenteritis in the UK resolves completely within a few days with supportive care, and viral illness has an excellent outcome. Prognosis worsens with delayed rehydration, very young age, comorbidity, immunosuppression, invasive bacterial disease, or complications such as HUS and shock.
Sources & References
🏥BMJ Best Practice(3)
💊BNF Drug References(1)
- Zanamivir[management.pharmacological]
✅NICE Guidelines(1)
- Gastroenteritis[overview]
📖Textbook References(1)
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 443)[context]