Treatment of Acute Gastroenteritis
Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration in acute gastroenteritis, with intravenous fluids reserved only for severe dehydration, shock, altered mental status, or ORS failure. 1, 2
Initial Assessment of Dehydration Status
Evaluate dehydration severity through specific physical examination findings 2:
- Mild dehydration (<4% body weight loss): Slightly decreased skin turgor, moist mucous membranes, normal vital signs 2
- Moderate dehydration (4-6% body weight loss): Decreased skin turgor, dry mucous membranes, sunken eyes, tachycardia, decreased urine output 1, 2
- Severe dehydration (>6% body weight loss): Markedly decreased skin turgor, very dry mucous membranes, altered mental status, weak pulse, poor perfusion, minimal urine output 1, 2
The most useful clinical predictors of ≥5% dehydration are abnormal capillary refill, abnormal skin turgor, and abnormal respiratory pattern 3. Laboratory testing is not routinely necessary for dehydration assessment 3.
Rehydration Protocol
Mild to Moderate Dehydration
Administer low-osmolarity ORS (such as Pedialyte or CeraLyte) as first-line therapy 2:
- Infants and children: 50-100 mL/kg over 3-4 hours 2
- Adolescents and adults: 2-4 L of ORS over 3-4 hours 2
- For children refusing oral intake: Consider nasogastric administration at 50-100 mL/kg over 3-4 hours 2
Critical pitfall: Do not use apple juice, Gatorade, or commercial soft drinks for rehydration—these are inappropriate due to high osmolarity and inadequate electrolyte composition 2.
ORS is equally effective as intravenous therapy for mild to moderate dehydration, with the added benefits of lower cost, fewer complications (no phlebitis risk), and shorter hospital stays 4, 5.
Severe Dehydration
Administer isotonic intravenous fluids (lactated Ringer's or normal saline) immediately 1, 2:
- Initial bolus: 20 mL/kg over 30 minutes 2
- Continue IV rehydration until pulse, perfusion, and mental status normalize (typically 2-4 hours) 1, 2
- Transition to ORS once the patient is alert, has no aspiration risk, and has no ileus to complete remaining deficit replacement 1, 2
IV fluids are also indicated for shock, altered mental status, failure of ORS therapy, or ileus 1.
Maintenance and Ongoing Loss Replacement
Once rehydrated, replace ongoing losses with ORS until diarrhea and vomiting resolve 1, 2:
- Children <10 kg: 60-120 mL ORS per diarrheal stool or vomiting episode (up to ~500 mL/day) 2
- Children >10 kg: 120-240 mL ORS per diarrheal stool or vomiting episode (up to ~1 L/day) 2
- Adolescents and adults: Ad libitum intake up to ~2 L/day 2
Nutritional Management
Continue breastfeeding throughout the diarrheal episode without interruption 1, 2. This is a strong recommendation with high-quality evidence.
Resume age-appropriate regular diet during or immediately after rehydration is completed 1, 2. Fasting or withholding food for 24 hours does not improve outcomes and should be avoided 2.
Pharmacological Adjuncts
Antiemetics
Ondansetron may be given to children >4 years of age and adolescents with significant vomiting to facilitate oral rehydration 1, 2:
- Dose: 0.15 mg/kg per dose 2
- Benefits: Reduces vomiting, improves ORS tolerance, decreases need for IV hydration and hospitalization 6, 3
Ondansetron is not routinely recommended for all cases but should be considered when vomiting interferes with oral rehydration 1, 7.
Antimotility Agents
Loperamide may be given to immunocompetent adults with acute watery diarrhea 1, 2:
- Dose: 4 mg initially, then 2 mg after each loose stool 2
- Contraindications: Never use in children <18 years of age 1, or in any patient with inflammatory diarrhea, fever, bloody stools, or suspected toxic megacolon 1, 8
Critical warning: Loperamide can cause serious cardiac adverse reactions including QT prolongation, Torsades de Pointes, cardiac arrest, and death, especially when taken at higher than recommended doses or with CYP3A4 inhibitors (itraconazole), CYP2C8 inhibitors (gemfibrozil), or P-glycoprotein inhibitors (quinidine, ritonavir) 8. Avoid in elderly patients taking QT-prolonging medications 8.
Probiotics and Zinc
Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent patients 1. The evidence is moderate quality.
Zinc supplementation (10-20 mg daily) reduces diarrhea duration in children 6 months to 5 years of age in areas with high zinc deficiency prevalence or in malnourished children 1.
When to Seek Further Care
Discontinue outpatient management and seek immediate medical attention if 2:
- No clinical improvement within 48 hours
- Blood in stools develops
- Fever or abdominal distention occurs
- Signs of severe dehydration develop
- Altered mental status or inability to tolerate any oral intake
Infection Control
Practice hand hygiene with soap and water after toilet use, diaper changes, before and after food preparation, and after animal contact 1, 2. Alcohol-based sanitizers are less effective against certain pathogens like norovirus; soap and water is preferred 1.
Healthcare settings require gloves, gowns, and strict hand hygiene when caring for patients with diarrhea 1, 2.