What is the recommended treatment for an adult patient with gastroenteritis?

Treatment of Gastroenteritis in Adults

The cornerstone of gastroenteritis treatment in adults is oral rehydration solution (ORS) for mild to moderate dehydration, with loperamide (4 mg initially, then 2 mg after each loose stool, maximum 16 mg/day) for symptomatic relief once adequate hydration is achieved. 1

Initial Assessment and Risk Stratification

Evaluate hydration status through clinical signs including:

• Skin turgor (prolonged tenting indicates moderate to severe dehydration) 1
• Mental status (altered consciousness suggests severe dehydration requiring IV therapy) 1
• Mucous membrane moisture 1
• Capillary refill time 1
• Vital signs (tachycardia, hypotension indicate severe dehydration) 1

Categorize dehydration severity:

• Mild (3-5% fluid deficit): Minimal clinical signs 1
• Moderate (6-9% fluid deficit): Dry mucous membranes, decreased skin turgor 1
• Severe (≥10% fluid deficit): Altered mental status, poor perfusion, shock 1

Rehydration Strategy

For Mild to Moderate Dehydration (Uncomplicated Cases)

Use low-osmolarity ORS as first-line therapy - it is as effective as intravenous therapy and strongly preferred over sports drinks or juices. 1, 2

• Administer 50-100 mL/kg ORS over 2-4 hours for moderate dehydration 1
• Replace ongoing losses: 10 mL/kg ORS for each watery stool 1
• Continue ORS until diarrhea and vomiting resolve 1
• Reassess hydration status after 2-4 hours 1

Common pitfall to avoid: Do not use sports drinks, apple juice, or other high-sugar beverages as primary rehydration solutions, as they can worsen diarrhea through osmotic effects. 1

For Severe Dehydration or Failed Oral Rehydration

Reserve intravenous rehydration for:

• Severe dehydration (≥10% fluid deficit) 1
• Shock or altered mental status 1
• Intractable vomiting despite antiemetics 1
• Failure of oral rehydration therapy 1

Use isotonic fluids (lactated Ringer's or normal saline) until pulse, perfusion, and mental status normalize, then transition to ORS. 1

Pharmacological Management

Symptomatic Relief with Loperamide

For immunocompetent adults with acute watery diarrhea, once adequately hydrated: 1, 3

• Initial dose: 4 mg orally 4
• Maintenance: 2 mg after every loose stool (maximum 16 mg/day) 4, 3

Critical contraindications for loperamide:

• Bloody diarrhea (risk of complications with invasive bacterial infections) 1
• High fever (suggests inflammatory/bacterial etiology) 1
• Suspected C. difficile infection 1
• Immunocompromised patients (until bacterial causes excluded) 4

Antiemetic Therapy

Ondansetron may be used to facilitate oral rehydration when vomiting is significant:

• Dose: 0.15 mg/kg (maximum 16 mg/dose) intramuscularly or intravenously 5
• Use only after adequate hydration is achieved 5
• Avoid in bloody diarrhea or suspected bacterial gastroenteritis 5

Important caveat: Ondansetron may increase stool volume while reducing vomiting - it facilitates rehydration but does not treat diarrhea itself. 6

Antimicrobial Therapy - When to Use

Antibiotics are NOT routinely indicated for most viral gastroenteritis cases. 1 However, consider antimicrobial therapy for:

Specific bacterial pathogens (when identified or strongly suspected):

• Salmonella with bacteremia: Ceftriaxone 2 g daily IV plus ciprofloxacin 500 mg twice daily IV, then de-escalate based on susceptibility 4
• Shigella: Fluoroquinolone (ciprofloxacin 500 mg twice daily PO) or azithromycin 500 mg daily 4
• Campylobacter: Azithromycin 500 mg daily (preferred due to 19% fluoroquinolone resistance) 4
• C. difficile infection:
  • Non-severe: Metronidazole 400 mg three times daily PO for 10 days OR vancomycin 125 mg four times daily PO for 10 days 4
  • Severe: Vancomycin 125 mg four times daily PO for 10 days 4

Clinical scenarios warranting empiric antibiotics: 1

• Bloody diarrhea with fever and systemic toxicity 4
• Recent antibiotic use (consider C. difficile) 1
• Recent foreign travel 1
• Immunocompromised state 4

Nutritional Management

Resume age-appropriate diet immediately during or after rehydration - early refeeding reduces illness severity and duration. 1

Foods to avoid:

• High simple sugar content (soft drinks, undiluted fruit juices) 1
• Caffeinated beverages (coffee, tea, energy drinks) - these worsen symptoms by stimulating intestinal motility 1
• High-fat foods 1

Continue normal eating - restrictive diets or prolonged fasting are not recommended. 1

Infection Control Measures

Implement strict hygiene protocols:

• Hand hygiene after toilet use, before eating, after handling soiled items 1
• Use gloves and gowns when caring for ill persons 1
• Clean and disinfect contaminated surfaces promptly 1
• Isolate ill persons until at least 2 days after symptom resolution 1

When to Hospitalize

Admit patients with:

• Severe dehydration (≥10% fluid deficit) 1
• Signs of shock (persistent tachycardia/hypotension despite initial resuscitation) 1
• Altered mental status 1
• Intractable vomiting despite antiemetics 1
• Bloody diarrhea with fever and systemic toxicity 1
• Significant comorbidities (elderly ≥65 years, immunocompromised) 1

Common pitfall: Elderly patients may not manifest classic dehydration signs but have higher mortality risk - use lower threshold for admission. 1

Medications to AVOID

Do NOT use:

• Antimotility agents in children <18 years (serious adverse events including deaths reported) 1
• Metoclopramide (Grade D recommendation - ineffective and potentially harmful) 1
• Adsorbents, antisecretory drugs, or toxin binders (no demonstrated effectiveness) 1