What is the primary treatment for a patient with gastroenteritis, considering symptoms and potential underlying medical conditions?

Treatment for Gastroenteritis

The primary treatment for gastroenteritis is immediate oral rehydration therapy (ORT) with low-osmolarity oral rehydration solution (ORS), which should be initiated without delay to correct and prevent dehydration, while antimicrobial therapy is reserved only for specific severe cases or identified bacterial pathogens. 1

Immediate Rehydration Strategy

Oral rehydration is the cornerstone of management and should never be delayed while awaiting diagnostic tests. 1 The approach depends on dehydration severity:

Mild to Moderate Dehydration (3-9% body weight loss)

• Administer 50-100 mL/kg of low-osmolarity ORS over 3-4 hours for infants and children 2
• Adolescents and adults should receive 2-4 L of ORS over 3-4 hours 2
• Use small, frequent volumes (5-10 mL every 1-2 minutes) to prevent triggering vomiting, gradually increasing as tolerated 3
• Children <10 kg: 60-120 mL ORS after each diarrheal stool (maximum ~500 mL/day) 1
• Children >10 kg: 120-240 mL ORS after each diarrheal stool (maximum ~1 L/day) 1

Severe Dehydration (≥10% body weight loss)

• Administer isotonic intravenous fluids (lactated Ringer's or normal saline) at 20 mL/kg boluses until pulse, perfusion, and mental status normalize 1, 2
• Switch to ORS once the patient can tolerate oral intake 1
• Nasogastric administration of ORS may be considered for moderate dehydration when oral intake is not tolerated 1

Nutritional Management

Resume age-appropriate diet immediately during or after rehydration is completed—do not delay feeding. 1, 2 This is critical because:

• Early refeeding reduces both severity and duration of illness 3
• There is no evidence that solid food delays recovery 1
• Continue breastfeeding throughout the diarrheal episode in infants 2
• Offer starches, cereals, soup, yogurt, vegetables, and fresh fruits 3
• Avoid fatty, heavy, spicy foods, caffeine, and lactose-containing foods if diarrhea is prolonged 1

Antiemetic Therapy

Ondansetron should be administered to children >4 years and adolescents with significant vomiting to facilitate oral rehydration. 2 This represents a shift from older guidelines:

• Dose: 0.15 mg/kg orally dissolving tablet 3
• Ondansetron reduces vomiting, improves ORS tolerance, and decreases need for IV hydration and hospitalization 1, 4, 5
• Recent evidence has changed guidelines to support ondansetron use, as it enhances compliance with ORT 5

Antimotility Agents: Critical Contraindications

Loperamide is absolutely contraindicated in children <18 years with acute diarrhea due to serious side effects including ileus, drowsiness, and potentially fatal abdominal distention. 1, 2, 3

For adults only:

• May use loperamide in immunocompetent adults with acute watery diarrhea once adequately hydrated 1, 2
• Initial dose: 4 mg orally, then 2 mg after each loose stool (maximum 16 mg/day) 1
• Avoid in inflammatory diarrhea, bloody diarrhea, or fever due to risk of complications 1

Antimicrobial Therapy: Highly Selective Use

Empiric antibiotics are NOT recommended for most cases of gastroenteritis. 1 Reserve antimicrobials only for:

Specific Indications for Antibiotics

• Infants <3 months with suspected bacterial etiology 1
• Immunocompromised patients with severe illness and bloody diarrhea 1
• Fever, abdominal pain, bloody diarrhea, and bacillary dysentery 1
• Identified bacterial pathogens with specific susceptibilities 1

Pathogen-Specific Treatment (when indicated)

• Campylobacter: Azithromycin 1
• Shigella: Ciprofloxacin or fluoroquinolone 1
• Salmonella: Ciprofloxacin, TMP-SMX, or amoxicillin 1

Critical Contraindication

Never give antibiotics for STEC O157 infections—they increase the risk of hemolytic uremic syndrome. 1

Adjunctive Therapies

Zinc Supplementation

• Reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency prevalence or in malnourished children 1, 2

Probiotics

• May be offered to reduce symptom severity and duration in immunocompetent patients 1

Red Flags Requiring Immediate Medical Evaluation

Seek immediate care for: 1

• No improvement within 48 hours
• Worsening symptoms or overall condition deterioration
• Severe vomiting preventing oral intake
• Persistent fever
• Frank blood in stools
• Abdominal distension
• Altered mental status
• Signs of severe dehydration (≥10% fluid deficit)

Infection Control Measures

Implement strict hand hygiene and contact precautions: 1, 2

• Hand hygiene after toilet use, diaper changes, before food preparation and eating
• Use gloves and gowns when caring for patients with diarrhea
• Separate ill persons from well persons until at least 2 days after symptom resolution 2
• Clean and disinfect contaminated surfaces promptly 2

Common Pitfalls to Avoid

1. Do not delay rehydration while waiting for diagnostic tests—start ORS immediately 1
2. Do not withhold food—early refeeding improves outcomes 3
3. Do not use antimotility agents in children or in adults with bloody diarrhea/fever 1, 3
4. Do not routinely prescribe antibiotics—they are indicated only in specific scenarios 1
5. Do not use antibiotics for STEC O157—this increases HUS risk 1

Monitoring and Follow-up

• Continue monitoring hydration status until symptoms resolve 1
• Reassess fluid and electrolyte balance, nutritional status if symptoms persist 1
• Modify or discontinue antimicrobial therapy when specific pathogen is identified 1