What is the recommended management of viral gastroenteritis, including rehydration strategy, medication use, diet, hygiene advice, and red‑flag criteria for children, adults, and high‑risk groups?

Management of Viral Gastroenteritis

Oral rehydration solution (ORS) with reduced osmolarity (<250 mmol/L) is the first-line treatment for all patients with mild-to-moderate dehydration, administered at 50–100 mL/kg over 2–4 hours, with intravenous fluids reserved only for severe dehydration, shock, altered mental status, or ORS failure. 1, 2

Rehydration Strategy

Mild-to-Moderate Dehydration (3–9% fluid deficit)

• Administer reduced-osmolarity ORS at 50 mL/kg for mild dehydration (3–5% deficit) or 100 mL/kg for moderate dehydration (6–9% deficit) over 2–4 hours 2, 3, 4
• ORS is superior to IV therapy—it is safer, less painful, less costly, and equally effective when oral intake is tolerated 2, 5
• For patients who cannot drink adequately but have intact mental status, nasogastric delivery of ORS is an acceptable alternative 2, 3
• Reassess hydration status after 2–4 hours of therapy 2, 3

Severe Dehydration (≥10% fluid deficit)

• Immediately initiate isotonic intravenous fluids (lactated Ringer's or normal saline) for severe dehydration, shock, altered mental status, failure of ORS therapy, or ileus 1, 2, 3
• Continue IV rehydration until pulse, perfusion, and mental status normalize, then transition to ORS to replace the remaining fluid deficit 1, 2
• In patients with ketonemia, an initial IV fluid bolus may be required before oral rehydration can be tolerated 1, 2

Ongoing Loss Replacement

• Replace each watery stool with 10 mL/kg of ORS and each vomiting episode with 2 mL/kg of ORS 2, 4
• For children <10 kg: 60–120 mL ORS per diarrheal stool or vomiting episode 3
• For children >10 kg: 120–240 mL ORS per diarrheal stool or vomiting episode 3
• Continue ORS replacement until diarrhea and vomiting resolve 1, 2

Nutritional Management

• Resume age-appropriate regular diet immediately during or after rehydration—do not withhold food 1, 2, 3
• Continue breastfeeding throughout the diarrheal episode in infants and children 1, 2, 3, 4
• Early refeeding prevents malnutrition and may reduce stool output 2
• Oral zinc supplementation (10–20 mg daily for 10–14 days) is recommended for children aged 6 months to 5 years in settings with high zinc-deficiency prevalence or when malnutrition is present 1, 2

Medication Use

Antiemetics

• Ondansetron may be given to children >4 years of age and adolescents with vomiting to facilitate oral rehydration 1, 2, 3, 4
• This adjunctive therapy can increase the success rate of oral rehydration and minimize the need for IV therapy 6

Antimotility Agents

• Antimotility drugs (loperamide) must never be given to children <18 years of age with acute diarrhea 1, 2, 3, 4
• Loperamide may be given to immunocompetent adults with acute watery diarrhea only after adequate hydration 1, 2
• Avoid loperamide at any age in patients with bloody diarrhea, fever, or suspected inflammatory diarrhea due to risk of toxic megacolon 1, 2

Probiotics

• Probiotic preparations may be offered to immunocompetent adults and children to reduce symptom severity and duration of infectious diarrhea 1, 2

Antimicrobials

• Empiric antibiotics are not recommended for viral gastroenteritis or most cases of acute watery diarrhea without recent international travel 2
• Antimicrobials are contraindicated for Shiga-toxin-producing E. coli infections (STEC O157) as they increase the risk of hemolytic-uremic syndrome 2

Hygiene and Prevention

• Perform hand hygiene after using the toilet, changing diapers, before and after preparing food, before eating, and after handling garbage, soiled laundry, or animals 1, 3
• Use gloves and gowns when caring for patients with diarrhea 1
• Hand hygiene with soap and water is preferred over alcohol-based sanitizers for certain pathogens (e.g., norovirus) 1
• Appropriate food safety practices prevent cross-contamination of other foods or cooking surfaces 1

Red-Flag Criteria Requiring Immediate Medical Attention

For All Patients

• Severe dehydration (≥10% fluid deficit): sunken eyes, decreased skin turgor, minimal urine output 3
• Altered mental status or toxic appearance 1, 2
• Shock or hemodynamic instability 2
• Failure of oral rehydration therapy 1, 2
• Intestinal ileus 1, 2

For Children

• Inability to tolerate oral fluids 3, 4
• Worsening signs of dehydration despite ORS 3, 4
• Bloody diarrhea 3, 4
• Significantly increasing fever 3, 4

High-Risk Groups Requiring Lower Threshold for Hospitalization

• Immunocompromised individuals 2
• Ill-appearing infants <3 months of age 2
• Patients with significant comorbidities 2

Common Pitfalls to Avoid

• Do not withhold food during or after rehydration—this delays recovery and may worsen malnutrition 1, 2
• Do not use antimotility agents in children or in any patient with bloody diarrhea or fever 1, 2
• Do not assume IV therapy is faster than ORS—studies show IV treatment often takes >5 hours in the emergency department, exceeding the 4-hour ORS protocol 7
• Do not give empiric antibiotics for uncomplicated viral gastroenteritis 2
• Do not use antimicrobials for suspected STEC infections 2