Management of Viral Acute Gastroenteritis (Stomach Flu)
Oral rehydration therapy is the cornerstone and first-line treatment for viral gastroenteritis, and is as effective as intravenous therapy for mild-to-moderate dehydration. 1, 2, 3
Immediate Clinical Assessment
Determine hydration status first - this drives all management decisions:
- Mild dehydration (3-5% fluid deficit): Increased thirst, slightly dry mucous membranes 1
- Moderate dehydration (6-9% fluid deficit): Loss of skin turgor, skin tenting when pinched, dry mucous membranes 1
- Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting (>2 seconds), cool/poorly perfused extremities, decreased capillary refill, rapid deep breathing (acidosis) 1
Key clinical features of viral gastroenteritis to confirm diagnosis:
- Acute onset with 12-48 hour incubation period 1
- Vomiting, non-bloody diarrhea, nausea, abdominal cramps 1
- Low-grade fever (high fever >39°C occurs in only one-third of cases) 4
- Self-limited course lasting 12-72 hours for norovirus or 3-8 days for rotavirus 1, 2
- Never bloody diarrhea - if present, this is NOT viral gastroenteritis 1, 4
Treatment Algorithm
For Mild-to-Moderate Dehydration (Most Cases)
Oral rehydration solution (ORS) is the definitive treatment:
- Provide ORS containing physiological concentrations of glucose and electrolytes 2
- Encourage 8-10 large glasses of clear liquids daily 4
- Eliminate lactose-containing products during acute illness 4
- ORS is as effective as IV therapy and should be first-line 1, 2, 3
Add ondansetron to facilitate oral rehydration when vomiting is prominent:
- A single oral dose of ondansetron reduces vomiting and facilitates ORT without significant adverse events 5
- Ondansetron increases success rate of oral rehydration and minimizes need for IV therapy and hospitalization 5, 2, 3
- Monitor QTc interval if using ondansetron, particularly with other QT-prolonging medications 4
- This represents a shift from older guidelines that discouraged antiemetics 3
For Severe Dehydration
Intravenous fluids are indicated only for:
- Severe dehydration with shock 4
- Altered mental status 4
- Failure of oral rehydration therapy 4
- Persistent vomiting preventing oral intake despite ondansetron 2
What NOT to Do
Avoid nonspecific antidiarrheal agents - they are ineffective and potentially harmful:
- Do NOT use adsorbents (kaolin-pectin), antimotility agents (loperamide), antisecretory drugs, or toxin binders 1
- These do not reduce diarrhea volume or duration 1
- Loperamide has caused severe abdominal distention and deaths in children 1
- These agents shift focus away from appropriate fluid and nutritional therapy 1
- Exception: Loperamide may be given to immunocompetent adults with acute watery diarrhea ONLY if no fever or inflammatory signs are present 4
Laboratory studies are rarely needed:
- Serum electrolytes only if clinical signs suggest abnormal sodium/potassium 1
- Stool cultures NOT indicated for typical viral gastroenteritis 1
- Basic labs (CBC, BMP, urinalysis) only for severe cases requiring hospitalization 4
Red Flags Requiring Immediate Re-evaluation
Return immediately or escalate care if:
- Bloody diarrhea develops - this excludes viral gastroenteritis 1, 4
- Bilious vomiting occurs - suggests obstruction or malrotation 4
- Fever exceeds 39°C or persists beyond 48 hours 4
- Signs of severe dehydration develop (decreased urination, dizziness, altered mental status) 4
- Symptoms persist beyond 1 week 6
- Abdominal pain localizes or worsens (consider appendicitis or other surgical pathology) 4
Expected Clinical Course
- Norovirus: symptoms resolve in 12-72 hours with viral shedding continuing up to 3 weeks 1
- Rotavirus: symptoms last 4-7 days with viral excretion for 8-14 days 1
- Approximately 10% seek medical attention; most resolve without treatment in otherwise healthy persons 1