Synopsis
Assess acute diarrhoea by physiological severity and exposure, correct fluid and electrolyte loss, obtain targeted stool microbiology and avoid antimicrobials or antimotility drugs when they increase harm.
- First decide whether the patient has shock, severe dehydration, sepsis or an acute surgical abdomen; organism naming comes later.
- Use oral rehydration solution for most conscious patients, replacing sodium and glucose together rather than relying on plain water.
- In adult shock give 500 mL crystalloid containing sodium 130 to 154 mmol/L over less than 15 minutes, then reassess before further boluses.
Key red flags
Shock, altered mental state, weak pulse, prolonged capillary refill or minimal urine output indicates severe intravascular depletion or sepsis.
Blood, mucus, fever, tenesmus and lower abdominal pain suggest colonic invasion or toxin injury and require stool testing.
Investigation priorities
Identify bacterial and selected viral pathogens in severe, bloody, persistent, imported or outbreak-associated diarrhoea.
Management branches
An adult presents with acute diarrhoea or vomiting.
- Check airway, breathing, circulation, mental state, capillary refill, postural symptoms and urine output and examine for peritonism or distension.
- Identify pregnancy, frailty, immune compromise, renal or cardiac disease and medicines that increase dehydration or acute kidney injury risk.
Key medicines
Oral rehydration solutionGive frequent small volumes prepared exactly to the product instructions, increasing intake to replace each loose stool and continuing as tolerated.
Intravenous crystalloid for shockGive 500 mL crystalloid containing sodium 130 to 154 mmol/L over less than 15 minutes in an adult, then reassess before repeating.