What is the likely diagnosis and recommended management for a patient presenting with acute gastroenteritis characterized by vomiting, watery diarrhea, and fever?

Acute Gastroenteritis with Vomiting, Diarrhea, and Fever

Likely Diagnosis

This presentation is most consistent with viral gastroenteritis, which accounts for approximately 70% of acute gastroenteritis cases, with norovirus being the leading pathogen in both adults and children. 1 The combination of vomiting, watery diarrhea, and fever after a typical 12-48 hour incubation period strongly suggests viral etiology. 1

• Norovirus is detected in 26% of adults with severe acute gastroenteritis, with symptoms typically resolving within 12-72 hours in immunocompetent hosts. 1
• Rotavirus accounts for 18% of cases in adults, characterized by diarrhea, vomiting, and fever lasting 4-7 days, though incidence has decreased dramatically in vaccinated children. 1, 2
• Bacterial causes should be suspected if high fever (>38.5°C), bloody stools, severe abdominal pain, or symptoms persisting beyond 3 days are present. 3, 1

Immediate Management Priorities

Assess Dehydration Severity

The physical examination is the most accurate method to determine hydration status and guide treatment intensity. 4

• Mild dehydration (3-5% body weight loss): Slightly dry mucous membranes, normal mental status, normal capillary refill. 5, 6
• Moderate dehydration (6-9% body weight loss): Dry mucous membranes, skin tenting, reduced urine output, mild lethargy. 5, 6
• Severe dehydration (≥10% body weight loss): Altered consciousness, prolonged skin tenting >2 seconds, cool extremities, poor capillary refill, rapid deep breathing—this is a medical emergency. 5, 6

The most reliable clinical predictors are prolonged skin retraction time, abnormal capillary refill, and rapid deep breathing. 5

Rehydration Strategy

Oral rehydration solution (ORS) is the first-line therapy for mild to moderate dehydration and is as effective as intravenous therapy. 3, 5, 6

For Mild to Moderate Dehydration:

• Administer low-osmolarity ORS using small, frequent volumes: Give 5-10 mL every 1-2 minutes via spoon or syringe—never allow rapid drinking from a cup, as this triggers vomiting and falsely suggests ORT failure. 5, 6
• Dosing for moderate dehydration: 100 mL/kg over 2-4 hours (for a 37 kg patient, this equals approximately 3,700 mL). 5
• Replace ongoing losses: 10 mL/kg for each watery stool and 2 mL/kg for each vomiting episode. 5, 6
• Reassess after 2-4 hours: If dehydration persists, recalculate deficit and restart rehydration. 5, 6
• Success rate exceeds 90% when proper small-volume technique is used. 5

For Severe Dehydration:

• Immediate intravenous rehydration is mandatory: Administer 20 mL/kg boluses of lactated Ringer's or normal saline until pulse, perfusion, and mental status normalize. 5, 6
• Hospital admission is required for all patients with severe dehydration. 5, 6
• Transition to ORS once mental status improves to replace remaining fluid deficit. 5

Antiemetic Therapy

Ondansetron should be considered for patients with significant vomiting that hinders oral rehydration therapy. 5, 6, 7

• A single oral dose of ondansetron reduces vomiting, facilitates ORT, and decreases hospitalization rates without significant adverse events. 7, 8, 4
• Ondansetron is recommended for children >4 years and adolescents with significant vomiting. 5, 6
• This medication increases ORT success and minimizes the need for intravenous therapy. 8

Nutritional Management

Resume an age-appropriate normal diet immediately during or after rehydration—do not withhold food or enforce fasting. 5, 6

• Early refeeding reduces illness severity, duration, and nutritional consequences. 5
• Recommended foods include starches (rice, potatoes, noodles), cereals, yogurt, fruits, and vegetables. 5
• Avoid: Soft drinks, undiluted apple juice, high-fat foods, and caffeinated beverages, as these worsen diarrhea through osmotic effects or delayed gastric emptying. 5, 6
• Continue breastfeeding throughout the illness in infants. 5, 6

Antimicrobial Therapy Decision

In most patients with acute watery diarrhea without recent international travel, empiric antimicrobial therapy is NOT recommended. 3

When to Consider Antibiotics:

• Bloody diarrhea with high fever and systemic toxicity suggesting bacterial dysentery (Shigella, Salmonella, Campylobacter). 3, 1, 9
• Watery diarrhea persisting >5 days. 5
• Positive stool culture identifying a treatable bacterial pathogen. 3, 9
• Immunocompromised patients or ill-appearing young infants. 3, 9

Important Caveats:

• The presence of fever alone does not mandate antibiotics—high fever (>38.5°C) with significant abdominal pain and duration >3 days suggests inflammatory bacterial infection warranting investigation. 3
• Empiric treatment provides only modest benefit (1 day shorter illness on average) and carries risks of antimicrobial resistance. 3
• Never use antibiotics if Shiga-toxin-producing E. coli (STEC) is suspected, as this increases the risk of hemolytic uremic syndrome. 5

Medications to Avoid

Loperamide and all antimotility agents are absolutely contraindicated in children <18 years due to risk of severe abdominal distension, ileus, and death. 3, 5, 6

• Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated. 5, 6
• Adsorbents, antisecretory drugs, and toxin binders are ineffective and should not be used. 3, 5
• Metoclopramide is explicitly contraindicated in gastroenteritis—it is a prokinetic agent that accelerates transit, which is counterproductive in diarrheal illness. 5

Red Flags Requiring Immediate Medical Attention

Recognize these warning signs that indicate severe disease or complications:

• Bilious (green) vomiting: Suggests possible intestinal obstruction requiring urgent surgical evaluation. 5
• Bloody stools with high fever: Indicates bacterial dysentery and risk of hemolytic uremic syndrome. 5, 1
• Altered mental status or severe lethargy: Sign of severe dehydration or sepsis. 5, 6
• Absent bowel sounds: Absolute contraindication to oral rehydration. 5
• Persistent tachycardia or hypotension despite initial fluid resuscitation. 5

Hospitalization Criteria

Admit patients with any of the following:

• Severe dehydration (≥10% deficit) or clinical shock. 5, 6
• Failure of oral rehydration therapy despite proper technique and antiemetic use. 5
• Altered mental status or intractable vomiting. 5
• Infants <3 months (lower threshold for complications). 5
• Bloody diarrhea with fever and systemic toxicity. 5
• Immunocompromised status or significant comorbidities. 5

Infection Control Measures

Implement strict infection control to prevent transmission:

• Practice proper hand hygiene after toilet use, diaper changes, and before food preparation. 5, 6
• Use gloves and gowns when caring for patients with diarrhea. 5, 6
• Clean and disinfect contaminated surfaces promptly. 5, 6
• Separate ill persons from well persons until at least 2 days after symptom resolution. 5, 6
• Asymptomatic contacts should not receive empiric or preventive therapy. 3

Common Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing—initiate ORT immediately based on clinical assessment. 5
• Do not use sports drinks, apple juice, or soft drinks as primary rehydration fluids; they lack appropriate electrolyte balance and may worsen diarrhea. 5, 4
• Do not allow rapid drinking from a cup—this is the most common reason for ORT failure. 5
• Do not withhold food or enforce prolonged fasting—early refeeding improves outcomes. 5, 6
• Stool cultures are rarely needed for typical watery diarrhea in immunocompetent patients; reserve for bloody diarrhea or prolonged symptoms. 5, 1