What is the recommended management of acute gastroenteritis in otherwise healthy children, adults, and elderly patients?

Treatment of Acute Gastroenteritis

Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration in children and adults with acute gastroenteritis, and should be initiated immediately without waiting for diagnostic testing. 1, 2, 3

Assessment of Dehydration Severity

Classify dehydration by clinical signs to determine the entire management pathway:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, normal mental status, normal vital signs 2
• Moderate dehydration (6-9% fluid deficit): Prolonged skin tenting >2 seconds, dry mucous membranes, reduced urine output, mild lethargy 1, 2
• Severe dehydration (≥10% fluid deficit): Altered consciousness, cool extremities, poor capillary refill, rapid deep breathing, shock—this is a medical emergency requiring immediate IV therapy 1, 2

The most reliable clinical predictors are abnormal capillary refill, prolonged skin retraction time, and rapid deep breathing—these correlate better with actual fluid deficit than sunken fontanelle or absent tears. 2, 4

Oral Rehydration Therapy (Mild to Moderate Dehydration)

Administer low-osmolarity ORS using small, frequent volumes to prevent vomiting:

• Give 5-10 mL every 1-2 minutes using a spoon, medicine cup, or syringe—never allow rapid drinking from a cup or bottle, as this triggers vomiting and falsely suggests ORT failure 2, 3
• For mild dehydration: 50 mL/kg ORS over 2-4 hours 2, 3
• For moderate dehydration: 100 mL/kg ORS over 2-4 hours 1, 2, 3
• Replace ongoing losses: 10 mL/kg for each watery stool and 2 mL/kg for each vomiting episode 1, 2
• Reassess hydration status after 2-4 hours; if still dehydrated, recalculate deficit and restart ORT 1, 2

Success rates exceed 90% when the small-volume, slow-administration technique is used correctly. 2

Use commercially available low-osmolarity ORS (Pedialyte, CeraLyte)—do not use sports drinks, apple juice, or soft drinks as they lack appropriate electrolyte balance and may worsen diarrhea through osmotic effects. 2, 3

Intravenous Rehydration (Severe Dehydration)

Severe dehydration is a medical emergency requiring immediate hospitalization and IV therapy:

• Administer 20 mL/kg boluses of lactated Ringer's or normal saline IV over 30 minutes, repeated until pulse, perfusion, and mental status normalize 1, 2, 3
• May require two IV lines or alternative vascular access (intraosseous, femoral) in shock 2
• Continue IV rehydration until the patient awakens, has no risk factors for aspiration, and has no evidence of ileus 1
• After mental status improves, transition to ORS to replace the remaining fluid deficit 1, 2, 3

Nutritional Management

Resume age-appropriate normal diet immediately during or after rehydration—do not withhold food or enforce fasting:

• Continue breastfeeding throughout the illness in infants 1, 2, 3
• Early refeeding with starches (rice, potatoes, noodles), cereals, yogurt, fruits, and vegetables reduces illness duration and improves nutritional outcomes 1, 2, 5
• Avoid foods high in simple sugars (soft drinks, undiluted fruit juice, gelatin), high-fat foods, and caffeinated beverages as they worsen diarrhea 2
• The BRAT diet may be used only briefly; it lacks adequate energy and protein for prolonged use 2

Pharmacological Management

Antiemetics

Ondansetron (0.15 mg/kg per dose) may be given to children >4 years and adolescents with significant vomiting to facilitate oral rehydration:

• Reduces vomiting, improves oral intake, decreases need for IV hydration, and shortens ED length of stay 1, 2, 3, 4, 6
• Very few serious side effects have been reported 4, 6

Antimotility Agents

Loperamide is absolutely contraindicated in all children <18 years with acute diarrhea due to risk of serious adverse events including ileus and death:

• Serious adverse events occurred in 6 of 28 children in controlled studies 1, 2

Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated:

• Initial dose 4 mg, then 2 mg after each loose stool, maximum 16 mg/day 1, 3, 7
• Avoid in inflammatory diarrhea, bloody diarrhea, fever, or suspected toxic megacolon 1, 3

Probiotics and Zinc

Probiotics may reduce symptom severity and duration in immunocompetent adults and children 1, 2

Zinc supplementation (10-20 mg/day) reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency prevalence or in malnourished children 1, 2

Antimicrobial Therapy

Routine antibiotics are not indicated because viral agents predominate in acute gastroenteritis:

• Consider antibiotics only when: bloody diarrhea with high fever and systemic toxicity (suggesting Shigella, Salmonella, Campylobacter), watery diarrhea persisting >5 days, positive stool culture for treatable bacterial pathogen, or immunocompromised host 1, 2
• Obtain stool culture before starting antibiotics in dysentery cases 2
• Avoid antibiotics if Shiga-toxin-producing E. coli (STEC) O157 is suspected due to risk of hemolytic-uremic syndrome 2

Hospitalization Criteria

Admit patients with any of the following:

• Severe dehydration (≥10% deficit) or clinical shock 1, 2, 3
• Failure of ORT despite proper small-volume technique and antiemetic use 1, 2
• Altered mental status or severe lethargy 1, 2
• Intractable vomiting despite ondansetron 2
• Infants <3 months (lower threshold due to higher complication risk) 1, 2
• Bloody diarrhea with fever and systemic toxicity (monitor for hemolytic-uremic syndrome) 1, 2
• Significant comorbidities or immunocompromised state 2

Lower the admission threshold for elderly patients (≥65 years) due to higher morbidity and mortality risk. 2

Critical Red-Flag Signs Requiring Immediate Evaluation

Bilious (green) vomiting suggests possible intestinal obstruction and requires urgent surgical assessment 2

Bloody stools with high fever suggest bacterial dysentery and risk of hemolytic-uremic syndrome 1, 2

Absent bowel sounds are an absolute contraindication to oral rehydration—do not give oral fluids until bowel sounds return 1, 2

Persistent tachycardia or hypotension despite initial fluid resuscitation requires admission 2

Infection Control Measures

Practice proper hand hygiene after using toilet, changing diapers, before and after food preparation, before eating, and after handling soiled items or animals 1, 2, 3

Use gloves and gowns when caring for patients with diarrhea 1, 2, 3

Clean and disinfect contaminated surfaces promptly 2

Separate ill persons from well persons until at least 2 days after symptom resolution 2

Common Pitfalls to Avoid

Do not delay rehydration while awaiting diagnostic testing—initiate ORT immediately based on clinical assessment 2

Do not allow patients to drink large volumes rapidly from a cup, as this triggers vomiting and gives the false impression that ORT has failed 2

Do not use sports drinks, apple juice, or soft drinks as primary rehydration fluids 2, 3

Do not withhold food or enforce prolonged fasting—early refeeding improves outcomes 1, 2, 5

Do not use antimotility agents, adsorbents, antisecretory drugs, or toxin binders in children, as they are ineffective and potentially harmful 1, 2

Do not underestimate dehydration in elderly patients, who may not manifest classic signs and have higher mortality risk 2