What is the appropriate management of acute gastroenteritis in an otherwise healthy adult?

Management of Acute Gastroenteritis in Otherwise Healthy Adults

For otherwise healthy adults with acute gastroenteritis, oral rehydration solution (ORS) is the first-line treatment for mild-to-moderate dehydration, with early resumption of a normal diet and avoidance of antimotility agents in cases with fever or bloody stools. 1

Initial Assessment and Risk Stratification

Evaluate hydration status immediately through clinical signs including skin turgor, mental status, mucous membrane moisture, capillary refill time, and vital signs to categorize dehydration severity: mild (3-5%), moderate (6-9%), or severe (≥10%). 1

• Obtain accurate current body weight; when premorbid weight is available, acute weight change provides the most precise fluid deficit estimate. 1
• Assess for red-flag features requiring immediate intervention: bloody diarrhea with fever, signs of severe dehydration (altered mental status, prolonged skin tenting >2 seconds, cool extremities, rapid deep breathing), or hemodynamic instability. 1
• Rule out non-gastrointestinal causes if fever is prominent—consider urinary tract infection, pneumonia, or other systemic infections. 1

Rehydration Strategy

Mild-to-Moderate Dehydration (First-Line Approach)

Administer low-osmolarity ORS as the cornerstone of therapy, which is as effective as intravenous rehydration for mild-to-moderate cases and successfully rehydrates >90% of patients. 1, 2

• For mild dehydration (3-5% deficit): Give 50 mL/kg ORS over 2-4 hours. 1
• For moderate dehydration (6-9% deficit): Give 100 mL/kg ORS over 2-4 hours. 1
• Use small, frequent volumes (5-10 mL every 1-2 minutes) via spoon or cup rather than allowing rapid large-volume drinking, which triggers vomiting and creates the false impression that oral rehydration has failed. 1
• Replace ongoing losses continuously: 10 mL/kg for each watery stool and 2 mL/kg for each vomiting episode. 1
• Reassess hydration status after 2-4 hours; if dehydration persists, recalculate deficit and restart ORS administration. 1

Severe Dehydration (Emergency Management)

Reserve intravenous rehydration for severe dehydration (≥10% deficit), shock, altered mental status, or failure of oral rehydration therapy. 1

• Administer isotonic fluids (lactated Ringer's or normal saline) in 20 mL/kg boluses until pulse, perfusion, and mental status normalize. 1
• Transition to ORS to replace remaining deficit once the patient improves. 1
• Hospital admission is mandatory for all patients with severe dehydration. 1

Nutritional Management

Resume a normal, age-appropriate diet immediately during or after rehydration—do not withhold food or enforce fasting, as early refeeding reduces illness severity and duration. 1

• Recommended foods include starches (rice, potatoes, noodles, crackers), cereals (unsweetened rice, wheat, oats), yogurt, cooked vegetables, and fresh fruits. 1
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice, gelatin, presweetened cereals) because they exacerbate diarrhea through osmotic effects. 1
• Limit high-fat foods, which delay gastric emptying. 1
• Limit or avoid caffeine (coffee, tea, caffeinated sodas, energy drinks), as caffeine stimulates intestinal motility and worsens diarrhea. 1

Pharmacological Management

Antimotility Agents

Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, but it is FDA-approved only for patients ≥2 years of age and should never be used in children <18 years. 1, 3

• Absolutely contraindicated in cases with fever, bloody diarrhea, or suspected bacterial dysentery due to risk of toxic megacolon and prolonged pathogen shedding. 1
• Do not use loperamide as a substitute for proper fluid and electrolyte therapy. 1

Antiemetics

Ondansetron may be considered in adults with significant vomiting to facilitate oral rehydration and reduce immediate need for intravenous fluids, though evidence is strongest in pediatric populations. 1, 2, 4

• Ondansetron improves tolerance of ORS and decreases hospitalization rates in the short term. 2, 4
• Potential adverse effect: may increase stool volume. 1

Antimicrobial Therapy

Routine antibiotics are not indicated because viral agents (norovirus, rotavirus) predominate and most cases are self-limited. 1, 5, 6

Consider antibiotics only in specific scenarios:

• Bloody diarrhea (dysentery) with high fever and systemic toxicity suggesting Shigella, Salmonella, or Campylobacter. 1
• Watery diarrhea persisting >5 days. 1
• Positive stool culture identifying a treatable bacterial pathogen. 1
• Immunocompromised host. 1
• Recent foreign travel or known exposure to specific pathogens. 1

Obtain stool culture before starting antibiotics in cases of suspected bacterial dysentery. 1

Do not use antibiotics if Shiga-toxin-producing E. coli (STEC) O157 is suspected due to increased risk of hemolytic-uremic syndrome. 1

Agents to Avoid

Do not use adsorbents (kaolin-pectin), antisecretory drugs, or toxin binders, as they do not reduce diarrhea volume or duration and divert focus from appropriate fluid and nutritional therapy. 1

Infection Control Measures

Practice rigorous hand hygiene after using the toilet, before eating, and after handling soiled items. 1

• Use gloves and gowns when caring for ill persons. 1
• Clean and disinfect contaminated surfaces promptly. 1
• Separate ill persons from well persons until at least 2 days after symptom resolution. 1

Hospitalization Criteria

Admit patients with any of the following:

• Severe dehydration (≥10% deficit) or clinical shock. 1
• Failure of oral rehydration therapy despite proper technique. 1
• Altered mental status or severe lethargy. 1
• Intractable vomiting despite antiemetic use. 1
• Bloody diarrhea with fever and systemic toxicity (monitor for hemolytic-uremic syndrome). 1
• Significant comorbidities or immunocompromised state. 1
• Lower the threshold for elderly patients (≥65 years) due to higher morbidity and mortality risk. 1

Critical Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing—initiate ORS immediately based on clinical assessment. 1
• Do not use sports drinks, apple juice, or soft drinks as primary rehydration fluids; they lack appropriate electrolyte balance and may worsen diarrhea. 1
• Do not withhold food or enforce prolonged fasting; this impairs intestinal recovery and worsens nutritional status. 1
• Do not give antimotility agents in the presence of fever, bloody stools, or suspected bacterial infection. 1
• Do not underestimate dehydration in elderly patients, who may not manifest classic signs and have higher mortality risk. 1
• Stool cultures are rarely needed for typical watery diarrhea in immunocompetent patients; reserve for dysentery, prolonged symptoms, or outbreak investigation. 1