Synopsis
Separate acute infection and dehydration from chronic inflammatory, malabsorptive, secretory and functional diarrhoea, select stool and endoscopic tests by consequence, and protect patients and contacts through appropriate public-health action.
- Define true diarrhoea by increased stool liquidity and frequency, then clarify onset, duration, volume, blood, nocturnal stool, urgency, steatorrhoea, pain and fasting response.
- Acute illness is commonly infectious, medicine-related or inflammatory; symptoms lasting four weeks or more require a structured chronic-diarrhoea pathway rather than repeated empirical antibiotics.
- Ask about travel, food and water, sick contacts, antibiotics, hospital or care-home exposure, sexual exposure, immunosuppression and occupation because testing and public-health consequences differ.
Key red flags
High fever, bloody stool, severe pain, dehydration, sepsis, recent travel, outbreak exposure or immunocompromise raises invasive infection and justifies urgent sampling, isolation and specialist or public-health discussion before empirical treatment.
Investigation priorities
Identify bacterial, viral or parasitic infection when severity, duration, travel, outbreak or host factors make the result actionable.
Management branches
Diarrhoea began recently and may be infectious.
- Assess perfusion, urine output, electrolytes, abdominal signs and host risk, giving oral rehydration or intravenous fluid according to severity.
- Institute appropriate enteric precautions and take an exposure history covering travel, food, contacts, antibiotics, healthcare, occupation and immune status.
Key medicines
Oral rehydration solutionGive frequent small volumes of a correctly prepared glucose-electrolyte solution, increasing replacement after each loose stool and using intravenous therapy if oral intake fails.
Oral vancomycin for first C difficile episodeNICE recommends 125 mg orally four times daily for 10 days for a first episode of mild, moderate or severe infection; follow the current recurrent-disease table.