Acute gastroenteritis is a rapid-onset inflammation of the stomach and small intestine, usually infectious, that resolves within a week in otherwise healthy people. It spans from mild, self-limited discomfort to dramatic fluid loss capable of producing hypovolemic shock within hours. Recognizing the varied faces of the illness guides fluid replacement, diet choices, and the decision to seek medical care.
- Core gastrointestinal features
• Nausea: an uneasy urge to vomit, often accompanied by increased salivation or retching.
• Vomiting: first gastric contents, then bile-tinged fluid; repeated every 30–60 min in severe cases, especially with viral or pre-formed toxin causes.
• Diarrhea: watery, occasionally rice-water or blood-flecked; defined as ≥3 loose stools per day or >200 g per stool for <14 days.
• Cramping abdominal pain: periumbilical or upper-mid, colicky waves that ease transiently after passing stool or flatus.
• Hyperactive bowel sounds: audible gurgling or splashing even without a stethoscope during active phases. - Systemic and dehydration clues
• Low-grade fever 37.5–38.5 °C common in viral and most bacterial cases; >39 °C suggests invasive organisms.
• Malaise, myalgia, headache: part of systemic cytokine response.
• Thirst, dry lips, coated tongue: early volume deficit.
• Sunken eyes, delayed skin turgor (>2 s), orthostatic dizziness: moderate dehydration.
• Irritability or lethargy in infants, absent tears, and sunken anterior fontanel: severe fluid loss. - Pathogen-group patterns
• Viral (rotavirus, norovirus): vomiting precedes diarrhea, fever mild, resolution in 3–5 days; outbreaks in schools, cruise ships, nursing homes.
• Pre-formed toxin (Staphylococcus aureus, Bacillus cereus): sudden onset within 6 h of contaminated food, intense vomiting, short total duration 12–24 h.
• Invasive bacteria (Salmonella, Shigella, Campylobacter): fever >38.5 °C, bloody stools, tenesmus, fecal leukocytes.
• Cholera-like: profuse painless “rice-water” stools, rapid dehydration, risk of shock within hours. - Red-flag combinations demanding urgent review
Persistent vomiting preventing any oral intake, bloody diarrhea with orthostatic hypotension, continuous abdominal rigidity or localized rebound tenderness, fever >39 °C with altered consciousness, and oliguria despite attempted rehydration.
Summary table
| Symptom cluster | Typical cause | Home-care threshold |
|---|---|---|
| Watery diarrhea, low fever | Viral | ORS 200 mL after each stool, resume solids when tolerated |
| Rice-water stools, no fever | Cholera | Seek care immediately; start oral rehydration en route |
| Bloody stools, high fever | Invasive bacteria | Medical review for stool culture and possible antibiotics |
| Vomiting every 30 min | Food-borne toxin | Small ice-chip sips; if unable to retain >8 h, visit ED |
| Sunken eyes, dizzy on standing | Dehydration | If urine dark/scant or mental state changes, go to hospital |