What is the recommended management of acute gastroenteritis in otherwise healthy adults and children, including assessment of dehydration severity, rehydration, antiemetics, anti‑diarrheal agents, antibiotics, probiotics, and criteria for hospitalization?

Management of Acute Gastroenteritis in Adults and Children

Rehydration: The Cornerstone of Treatment

Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration in both children and adults with acute gastroenteritis, and should be initiated immediately without waiting for diagnostic testing. 1, 2

Assessment of Dehydration Severity

Evaluate hydration status through specific clinical signs to categorize dehydration 2, 3:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, normal mental status, normal vital signs 2
• Moderate dehydration (6-9% fluid deficit): Loss of skin turgor with tenting when pinched, dry mucous membranes, decreased urine output 2
• Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting (>2 seconds), cool and poorly perfused extremities, decreased capillary refill, rapid deep breathing indicating acidosis 2

The most reliable clinical predictors of significant dehydration are abnormal capillary refill, abnormal skin turgor, abnormal respiratory pattern, and prolonged skin retraction time >2 seconds 2, 4. Acute weight change is the most accurate assessment when premorbid weight is known 2.

Oral Rehydration Protocol

For mild to moderate dehydration, administer low-osmolarity ORS using the following protocol 1, 2:

• Children/infants: 50-100 mL/kg over 2-4 hours 2, 3
• Adolescents/adults: 2-4 L over 2-4 hours 3
• Technique: Start with small volumes (5-10 mL every 1-2 minutes) using a spoon or syringe, gradually increasing as tolerated to prevent triggering more vomiting 2
• Replace ongoing losses: Administer 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 2
• Continue ORS until clinical dehydration is corrected and to replace ongoing losses until diarrhea and vomiting resolve 1

Critical pitfall to avoid: Do not use sports drinks, apple juice, or other inappropriate fluids as primary rehydration solutions for moderate to severe dehydration, as they lack appropriate electrolyte composition and high sugar content can worsen diarrhea through osmotic effects 2.

Nasogastric Rehydration

Nasogastric administration of ORS may be considered in patients with moderate dehydration who cannot tolerate oral intake, refuse to drink adequately, or are too weak but have normal mental status 1, 2.

Intravenous Rehydration

Reserve intravenous rehydration for specific indications 1, 2:

• Severe dehydration (≥10% fluid deficit)
• Shock or altered mental status
• Failure of oral rehydration therapy
• Ileus (absent bowel sounds)
• Intractable vomiting despite antiemetics

IV protocol: Administer isotonic fluids (lactated Ringer's or normal saline) at 20 mL/kg over 30 minutes for severe dehydration 2, 3. Continue IV rehydration until pulse, perfusion, and mental status normalize, then transition to ORS to replace remaining deficit 1, 2.

Nutritional Management

Resume age-appropriate diet during or immediately after rehydration is completed—early refeeding reduces severity and duration of illness 1, 2, 3.

• Continue breastfeeding throughout the diarrheal episode in infants 1, 2, 3
• Avoid fasting or restrictive diets 2, 3
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice), high-fat foods, and caffeinated beverages as they can exacerbate diarrhea 2

Pharmacological Management

Antiemetics

Ondansetron may be given to children >4 years and adolescents with significant vomiting to facilitate oral rehydration 1, 2, 3. Ondansetron reduces vomiting, improves oral intake success, decreases need for IV rehydration, and shortens emergency department stay with minimal adverse effects 4, 5, 6.

Dosing: 0.15 mg/kg orally dissolving tablet 7

Antimotility Agents

Loperamide should NOT be given to children <18 years with acute diarrhea due to serious adverse events including ileus, drowsiness, and potentially fatal abdominal distention 1, 2, 3.

Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, but should be avoided in suspected inflammatory diarrhea, bloody diarrhea, or diarrhea with fever where toxic megacolon may result 1, 2, 3.

Critical pitfall: Metoclopramide has no role in gastroenteritis management and should not be used, as it is a prokinetic agent that accelerates transit—counterproductive when the goal is to reduce stool output 2.

Probiotics

Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent adults and children with infectious or antimicrobial-associated diarrhea 1, 2.

Zinc Supplementation

Zinc supplementation reduces diarrhea duration in children 6 months to 5 years of age in areas with high zinc deficiency prevalence or in malnourished children 2, 3.

Antimicrobial Therapy

In most people with acute watery diarrhea without recent international travel, empiric antimicrobial therapy is NOT recommended 1. Antimicrobial agents have limited usefulness since viral agents are the predominant cause 2.

Exceptions where empiric treatment may be considered 1:

• Immunocompromised patients
• Young infants who are ill-appearing
• Bloody diarrhea with fever and systemic toxicity

Avoid antimicrobial therapy in suspected or proven STEC infections (particularly those producing Shiga toxin 2) as it may increase risk of hemolytic uremic syndrome 1.

Criteria for Hospitalization

Admit patients with acute gastroenteritis who meet the following criteria 2:

• Severe dehydration (≥10% fluid deficit) requiring IV rehydration 2, 7
• Signs of shock or persistent tachycardia/hypotension despite initial fluid resuscitation 2
• Altered mental status 2, 7
• Failure of oral rehydration therapy after ondansetron trial 2, 7
• Intractable vomiting preventing adequate oral intake 2, 7
• Ileus (absent bowel sounds) 2, 7
• Bloody diarrhea with fever and systemic toxicity suggesting dysentery or risk of hemolytic uremic syndrome 2

High-Risk Populations Requiring Lower Threshold for Admission

• Infants <3 months due to higher risk of severe dehydration and complications 2
• Elderly patients (≥65 years) who have higher percentages of hospitalization and death, and may not manifest classic signs of dehydration 2
• Immunocompromised patients (on immunosuppressive therapy, HIV-infected, transplant recipients, malignancy) due to risk of severe or prolonged illness 2

Critical pitfall: Do not underestimate dehydration in elderly patients who may not manifest classic signs and have higher mortality risk 2.

Red Flags Requiring Immediate Medical Attention

• Severe lethargy or altered consciousness 2
• Prolonged skin tenting >2 seconds 2
• Cool extremities with decreased capillary refill 2
• Rapid, deep breathing indicating metabolic acidosis 2
• Bloody stools with fever and systemic toxicity 2
• Persistent vomiting despite small-volume ORS administration 2
• Absent bowel sounds on auscultation 2
• Stool output >10 mL/kg/hour (though ORT should still be attempted) 2

Infection Control Measures

Implement strict infection control to prevent transmission 2, 3:

• Practice proper hand hygiene after using toilet, changing diapers, before food preparation, before eating, and after handling soiled items 2, 3
• Use gloves and gowns when caring for people with diarrhea 2, 3
• Clean and disinfect contaminated surfaces promptly 2, 3
• Separate ill persons from well persons until at least 2 days after symptom resolution 2, 3

Asymptomatic contacts should not be offered empiric or preventive therapy, but should follow appropriate infection prevention measures 1.