Diarrhea
Acute diarrhea is three or more loose stools in 24 hours, per the ACG 2016 guideline, and is usually self-limited.
Symptoms
Frequent loose or watery stools, cramping, and sometimes nausea, fever, or blood in the stool -- the presence of blood or high fever changes management meaningfully.
Causes and risk
Viruses cause most cases; bacterial causes (including foodborne illness) and travel-associated infections are next most common. Recent antibiotic use raises concern for C. difficile.
How it is evaluated
Most acute diarrhea needs no testing. Stool studies are reserved for bloody or mucoid stools, severe abdominal pain, signs of sepsis, fever, or symptoms lasting beyond about a week (or two weeks for travel-associated cases), per 2017 IDSA guidance. When testing is needed, molecular/PCR panels are now preferred over routine culture per 2024 IDSA/ASM guidance.
Treatment
Oral rehydration is the cornerstone of treatment. Loperamide should be avoided in bloody or inflammatory diarrhea due to toxic megacolon risk; bismuth subsalicylate is a safer alternative in that setting. Antibiotics are not routine and should specifically be avoided in immunocompetent bloody diarrhea without signs of sepsis; they're reserved for sepsis, moderate-to-severe travelers' diarrhea, or a specific identified pathogen that needs targeted therapy.
When to seek care
Signs of dehydration (dizziness, reduced urination, extreme thirst), high fever, bloody stools, or symptoms suggesting sepsis need urgent evaluation rather than continued home management.