Gastroenteritis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infection, leading to diarrhoea, vomiting, abdominal pain, and dehydration.

Aetiology

1. Viral Causes (Most Common):

• Norovirus: highly contagious, common in outbreaks (e.g., cruise ships, hospitals).
• Rotavirus: leading cause in children, now reduced due to vaccination.
• Adenovirus: affects infants and young children.

2. Bacterial Causes:

• Salmonella: from undercooked poultry, eggs.
• Escherichia coli (E. coli): enterotoxigenic strain (traveller’s diarrhoea), Shiga-toxin-producing strain (E. coli O157:H7) causing haemolytic uraemic syndrome.
• Campylobacter: found in contaminated poultry, dairy.
• Shigella: causes dysentery (bloody diarrhoea).
• Clostridioides difficile: antibiotic associated diarrhoea, common in hospital settings.

3. Parasitic Causes:

• Giardia lamblia: contaminated water sources.
• Cryptosporidium: waterborne outbreaks.

Pathophysiology

• Infectious agents invade or produce toxins that damage the intestinal mucosa.
• Leads to increased secretion of electrolytes and water into the intestines.
• Results in diarrhoea, dehydration, and possible electrolyte imbalance.

Risk factors

• Contaminated food or water consumption.
• Recent travel to endemic areas.
• Close contact with infected individuals.
• Young children and elderly (higher risk of dehydration).
• Use of proton pump inhibitors (reduces stomach acid, increasing susceptibility).
• Immunosuppression (HIV, chemotherapy).
• Recent antibiotic use (risk of C. difficile infection).

Signs and symptoms

• Diarrhoea: watery in viral causes, bloody in bacterial causes (e.g., Shigella, E. coli O157).
• Vomiting: more common in viral gastroenteritis.
• Abdominal cramps.
• Fever: common in bacterial infections.
• Signs of dehydration: dry mucous membranes, reduced urine output, tachycardia.

Investigations

• Clinical diagnosis: based on history and symptoms.
• Stool culture: indicated if:
  • Severe or prolonged symptoms (>7 days).
  • Bloody diarrhoea (rule out bacterial dysentery).
  • Recent travel history (check for parasites).
  • Hospital-acquired diarrhoea (test for C. difficile toxin).
• Blood tests:
  • Urea and electrolytes (assess dehydration, hypokalaemia).
  • Full blood count (raised white cells suggest bacterial infection).

Management

1. Supportive Care:

• Oral rehydration therapy (ORT): first-line for mild to moderate dehydration (e.g., Dioralyte®).
• IV fluids: if severe dehydration or unable to tolerate oral fluids.
• Antipyretics: paracetamol for fever.
• Antiemetics: consider ondansetron if persistent vomiting.

2. Specific Treatment:

• Viral gastroenteritis: supportive care; avoid antibiotics.
• Bacterial gastroenteritis: most cases are self-limiting, but antibiotics may be needed for:
  • Severe or persistent symptoms.
  • Immunocompromised patients.
  • Specific infections (e.g., ciprofloxacin for severe traveller’s diarrhoea).
• Parasitic infections: metronidazole for Giardia.

3. Prevention:

• Hand hygiene (soap and water, alcohol-based hand sanitisers).
• Safe food handling and proper cooking.
• Vaccination (e.g., rotavirus vaccine in infants).
• Boil or treat drinking water when travelling.