What is the management approach for a patient presenting with acute gastroenteritis?

Management of Acute Gastroenteritis

Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration, and should be initiated immediately using small, frequent volumes (5-10 mL every 1-2 minutes) to successfully rehydrate >90% of patients without requiring intravenous therapy. 1

Initial Assessment and Hydration Status

Evaluate dehydration severity through specific clinical signs rather than waiting for laboratory results 1:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, normal vital signs, adequate urine output 1
• Moderate dehydration (6-9% fluid deficit): Loss of skin turgor with tenting when pinched, dry mucous membranes, decreased urine output, mild tachycardia 1, 2
• Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting (>2 seconds), cool and poorly perfused extremities, decreased capillary refill, rapid deep breathing indicating acidosis 1

The most reliable clinical predictors are prolonged skin retraction time, abnormal capillary refill, and rapid deep breathing—more accurate than sunken fontanelle or absence of tears 1. Acute weight change is the most accurate assessment if premorbid weight is known 2.

Rehydration Protocol

Oral Rehydration Therapy (First-Line)

For mild to moderate dehydration, administer low-osmolarity ORS using the following protocol 1:

• Start with 5-10 mL every 1-2 minutes using a spoon or syringe to prevent triggering vomiting 1
• Gradually increase volume as tolerated 1
• For moderate dehydration: Give 100 mL/kg ORS over 2-4 hours 1
• Replace ongoing losses continuously: 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1
• Reassess hydration status after 2-4 hours; if still dehydrated, reestimate deficit and restart rehydration 1

Use low-osmolarity ORS formulations rather than sports drinks, apple juice, or soft drinks, as these have inappropriate osmolarity and can worsen osmotic diarrhea through their high simple sugar content 1. Nasogastric administration may be considered for patients who cannot tolerate oral intake or refuse to drink adequately 1.

Intravenous Rehydration (Reserved for Specific Indications)

Reserve IV rehydration for 1:

• Severe dehydration (≥10% fluid deficit)
• Shock or hemodynamic instability
• Altered mental status
• Failure of oral rehydration therapy after 2-4 hours
• Ileus (absent bowel sounds)
• Intractable vomiting despite antiemetics

Use isotonic fluids such as lactated Ringer's or normal saline 1. Continue IV rehydration until pulse, perfusion, and mental status normalize, then transition to ORS to replace remaining deficit 1.

Nutritional Management

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

• Continue breastfeeding in infants throughout the diarrheal episode 1
• Do not use restrictive diets or prolonged fasting 1
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice), high-fat foods, and caffeinated beverages as they can exacerbate diarrhea through osmotic effects and increased intestinal motility 1

Pharmacological Management

Antiemetics

Ondansetron may be given to children >4 years and adults to facilitate oral rehydration when vomiting is significant 1. This decreases the rate of vomiting, improves oral intake success, reduces need for IV hydration, and shortens emergency department stay 3, 4.

Antimotility Agents

Loperamide is absolutely contraindicated in children <18 years with acute diarrhea due to serious adverse events including ileus and deaths 1. Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated 1.

Agents to Avoid

Do not use the following as they lack effectiveness 1:

• Adsorbents
• Antisecretory drugs
• Toxin binders
• Metoclopramide (Grade D recommendation: fair evidence it is ineffective or harms outweigh benefits) 1

Probiotics and Zinc

Probiotics may reduce symptom severity and duration in both adults and children 1. Zinc supplementation reduces diarrhea duration in children 6 months to 5 years of age in areas with high zinc deficiency prevalence or in malnourished children 1.

Antimicrobial Therapy

Antimicrobial agents have limited usefulness since viral agents are the predominant cause 1. Consider antimicrobial therapy only in specific cases 1, 5:

• Bloody diarrhea with fever and systemic toxicity
• Recent antibiotic use (consider Clostridioides difficile)
• Exposure to certain pathogens
• Recent foreign travel
• Immunodeficiency or severe illness
• Chronic conditions or specific risk factors

Empiric therapy may be started with oral co-trimoxazole or metronidazole, but in severe cases parenteral treatment with ceftriaxone or ciprofloxacin might be considered 5.

Infection Control Measures

Implement strict infection control to prevent transmission 1:

• Practice proper hand hygiene after using toilet or changing diapers, before and after food preparation, before eating, and after handling soiled items 1
• Use gloves and gowns when caring for people with diarrhea 1
• Clean and disinfect contaminated surfaces promptly 1
• Separate ill persons from well persons until at least 2 days after symptom resolution 1

Admission Criteria

Hospitalize patients with the following 1, 2:

• Severe dehydration (≥10% fluid deficit)
• Signs of shock or persistent hemodynamic instability despite initial fluid resuscitation
• Failure of oral rehydration therapy after 2-4 hours of appropriate ORS administration
• Altered mental status
• Intractable vomiting despite antiemetics
• Ileus (absent bowel sounds)
• Significant comorbidities increasing risk of complications

Use lower thresholds for admission in high-risk populations 1:

• Elderly patients (≥65 years) due to higher mortality risk
• Immunocompromised patients (immunosuppressive therapy, HIV-infected, transplant recipients, malignancy)
• Infants <3 months given higher risk of severe dehydration and complications

Red Flags Requiring Urgent Evaluation

Seek immediate medical attention for 1, 2:

• Duration >7 days: Typical viral gastroenteritis resolves within 5-7 days; prolonged symptoms require stool studies including culture, ova and parasites 2
• Bloody stools with fever and systemic toxicity (may indicate Salmonella, Shigella, enterohemorrhagic E. coli) 1
• Persistent tachycardia despite adequate rehydration suggests underlying pathology 2
• Severe abdominal pain disproportionate to examination findings 1
• Stool output >10 mL/kg/hour (associated with lower ORT success rates, though ORT should still be attempted) 1

Common Pitfalls to Avoid

• Do not delay rehydration therapy while awaiting diagnostic testing—initiate ORS promptly 1
• Do not use inappropriate fluids like apple juice or sports drinks as primary rehydration solutions for moderate to severe dehydration 1
• Do not administer antimotility drugs to children or in cases of bloody diarrhea 1
• Do not unnecessarily restrict diet during or after rehydration 1
• Do not underestimate dehydration in elderly patients, who may not manifest classic signs and have higher mortality risk 1
• Do not give metoclopramide—it is a prokinetic agent that accelerates transit and is counterproductive in diarrheal illness 1