Gastroenteritis in adults
Introduction
Gastroenteritis is an acute, usually self‑limited inflammatory disorder of the gastrointestinal tract caused by enteric pathogens (viruses, bacteria or parasites) or their toxins. It is defined clinically by the sudden onset of diarrhoea, with or without vomiting, abdominal pain and systemic symptoms.
Most presentations to the emergency department (ED) are uncomplicated and managed with rehydration and advice; a minority require admission, targeted antimicrobials, or public‑health action.
Key pathogens and epidemiology
- Viral causes are the most common aetiology in adults; norovirus is the single most frequent cause in the UK and is highly infectious with seasonal peaks in colder months (UKHSA/GOV.UK).
- Rotavirus and adenovirus occur less commonly in adults than in children.
- Bacterial pathogens commonly cause food‑borne or person‑to‑person infection; important organisms include Campylobacter, Salmonella, Shigella, pathogenic E. coli (including STEC/VTEC), Clostridioides difficile (often following antibiotics), Bacillus cereus, Staphylococcus aureus and Yersinia spp.
- Parasitic causes to consider with relevant exposures include Giardia, Entamoeba histolytica and Cryptosporidium.
- Mechanisms of diarrhoea include secretory diarrhoea from enterotoxins, cytotoxin‑mediated mucosal injury, and direct mucosal invasion producing inflammatory (often bloody) diarrhoea.
Initial priorities in the ED
- Rapidly assess airway, breathing and circulation and identify shock or sepsis and begin resuscitation as required.
- Assess degree of dehydration, ability to tolerate oral fluids, and the need for IV therapy.