What is the appropriate management for an otherwise healthy adult with acute gastroenteritis?

Management of Acute Gastroenteritis in Otherwise Healthy Adults

Oral rehydration solution (ORS) administered in small, frequent volumes (5-10 mL every 1-2 minutes) is the cornerstone of treatment for mild to moderate dehydration, with immediate resumption of normal diet once rehydrated. 1, 2

Initial Assessment and Hydration Status

Evaluate dehydration severity through specific clinical markers rather than waiting for laboratory confirmation:

• Mild dehydration (3-5% body weight loss): Slightly dry mucous membranes, normal mental status, adequate urine output 1, 3
• Moderate dehydration (6-9% body weight loss): Dry mucous membranes, decreased skin turgor with tenting, reduced urine output, mild tachycardia 1, 2
• Severe dehydration (≥10% body weight loss): Altered mental status, prolonged capillary refill (>2 seconds), hypotension, minimal or no urine output, cool extremities 1, 2

The most accurate assessment is acute weight change when premorbid weight is known, though this is rarely available in practice. 2

Rehydration Strategy

For Mild to Moderate Dehydration

Use commercially available low-osmolarity ORS as first-line therapy—not sports drinks, sodas, or fruit juices, which lack appropriate electrolyte balance and contain excess simple sugars that worsen diarrhea through osmotic effects. 1, 2

Administration technique is critical to success:

• Start with 5-10 mL every 1-2 minutes using a spoon, medicine cup, or syringe 2, 3
• Gradually increase volume as tolerated without triggering vomiting 2
• For adults with moderate dehydration: administer 2-4 liters ORS over 3-4 hours 3
• Replace ongoing losses: 10 mL/kg (approximately 700-800 mL for average adult) for each watery stool and 2 mL/kg (approximately 150 mL) for each vomiting episode 2

The most common error is allowing patients to drink large volumes rapidly from a cup or bottle, which provokes vomiting and creates the false impression that oral rehydration has failed. Success rates exceed 90% when the small-volume, slow-administration method is used correctly. 2

For Severe Dehydration

Administer isotonic intravenous fluids (lactated Ringer's or normal saline) immediately for severe dehydration, shock, altered mental status, or failure of oral rehydration therapy. 1, 3

• Continue IV rehydration until pulse, perfusion, and mental status normalize 1
• Transition to ORS to replace remaining deficit once patient improves 1, 2
• In patients with ketonemia, an initial course of IV hydration may be needed to enable tolerance of oral rehydration 1

Nutritional Management

Resume normal, age-appropriate diet immediately during or after rehydration—do not fast or restrict food. 1, 2, 3

Early refeeding reduces severity, duration, and nutritional consequences of diarrheal illness. 2

Avoid these dietary items during active illness:

• Foods high in simple sugars (soft drinks, undiluted fruit juices) that exacerbate diarrhea through osmotic effects 2
• Caffeinated beverages (coffee, tea, energy drinks) that worsen symptoms by stimulating intestinal motility and accelerating transit time 2
• High-fat foods during the acute phase 2

Pharmacological Management

Antimotility Agents

Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, but only after excluding contraindications. 1, 3, 4

Absolute contraindications to loperamide:

• Bloody diarrhea or fever suggesting inflammatory/invasive diarrhea (risk of toxic megacolon) 1
• Suspected or confirmed Shigella, Salmonella, enterohemorrhagic E. coli, or C. difficile infection 1
• Ileus or abdominal distention 1

Critical safety warnings:

• Use only the prescribed dosage; higher doses can cause serious cardiac arrhythmias including QT prolongation and Torsades de Pointes 4
• Avoid in patients taking CYP3A4 inhibitors (itraconazole), CYP2C8 inhibitors (gemfibrozil), or P-glycoprotein inhibitors (quinidine, ritonavir) as these increase loperamide exposure 2-13 fold 4
• Avoid in patients with underlying cardiac conditions or those taking Class IA/III antiarrhythmics 4
• Seek immediate medical care if fainting, rapid/irregular heartbeat, or unresponsiveness occurs 4

Antiemetics

Ondansetron may be considered to facilitate oral rehydration in adults with significant vomiting, though it is not a substitute for proper fluid therapy. 1, 5, 6, 7

Ondansetron reduces vomiting, improves tolerance of ORS, and decreases need for IV rehydration without significant adverse events. 5, 6, 7

Probiotics

Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent adults with infectious diarrhea. 1, 3

What NOT to Use

Do not use antimotility agents, adsorbents, antisecretory drugs, or toxin binders as primary therapy—they do not reduce diarrhea volume or duration and divert focus from appropriate fluid and nutritional therapy. 2

Never use metoclopramide in gastroenteritis management—it is a prokinetic agent that increases GI motility, which is counterproductive when the goal is to reduce stool output. 2

Red Flags Requiring Immediate Medical Evaluation

Seek emergency care if any of the following develop:

• Bloody diarrhea with fever and systemic toxicity (suggests Salmonella, Shigella, enterohemorrhagic E. coli; risk of hemolytic uremic syndrome) 1, 2
• Altered mental status, severe lethargy, or confusion (indicates severe dehydration or electrolyte abnormalities) 1, 2
• Persistent vomiting despite small-volume ORS administration (indicates failure of oral rehydration therapy) 2
• Signs of severe dehydration: prolonged capillary refill, cool extremities, rapid deep breathing, minimal urine output 2
• Severe abdominal pain disproportionate to examination findings (consider surgical abdomen) 2
• No clinical improvement after 48 hours of appropriate home management 4

Infection Control Measures

Practice rigorous hand hygiene to prevent transmission:

• After using the toilet 1, 3
• Before and after preparing food 1, 3
• Before eating 1, 3
• After handling garbage or soiled laundry 1, 3

Separate ill persons from well persons until at least 2 days after symptom resolution. 3

Clean and disinfect contaminated surfaces promptly with appropriate disinfectants. 2, 3

Common Pitfalls to Avoid

• Delaying rehydration while awaiting diagnostic testing—begin ORS immediately based on clinical assessment 2
• Using inappropriate fluids (sports drinks, sodas, apple juice) as primary rehydration solutions 2
• Allowing rapid, large-volume drinking instead of small, frequent sips 2
• Restricting diet during or after rehydration 1, 2
• Prescribing antimotility agents when bloody diarrhea, fever, or inflammatory features are present 1
• Using loperamide at higher than recommended doses or in combination with CYP3A4/CYP2C8/P-glycoprotein inhibitors 4
• Relying on antiemetics or antimotility agents as substitutes for proper fluid and electrolyte therapy 1, 2