Viral gastroenteritis is a self-limited syndrome of rapid-onset nausea, vomiting, watery (non-bloody, non-mucoid) diarrhea, and cramping abdominal pain caused most commonly by norovirus, rotavirus, sapovirus, astrovirus, and enteric adenovirus. [1] It is the most common cause of acute nausea and vomiting and accounts for the majority of acute diarrheal illness in developed countries. [2-3] The cornerstone of management is oral rehydration and early refeeding; antibiotics are not indicated. [1][3]
1. History
- Onset and timeline: Abrupt onset typically 24–48 hours after exposure; preformed toxin food poisoning has a shorter incubation (2–7 hours) [4]
- Symptom characterization: Watery, non-bloody, non-mucoid diarrhea; nausea and vomiting (often predominant); diffuse crampy abdominal pain; malaise [1]
- Volume assessment: Quantify oral intake, urine output, number of emesis/diarrheal episodes, last void
- Exposures: Sick contacts, daycare/institutional setting, cruise ship, recent food (shellfish, salad bars, buffets), contaminated water [5]
- Important negatives: Absence of bloody stool, high fever, severe focal abdominal pain, and tenesmus makes viral etiology more likely [3-4]
- Medications: Recent antibiotics (C. difficile risk), PPIs, chemotherapy, laxatives [4]
- Travel history: International travel raises concern for bacterial/parasitic causes [3]
2. Alarm Features
- Bloody or mucoid stools → suggests inflammatory/invasive bacterial pathogen [3]
- High fever ≥38.5°C (101.3°F) → suggests bacterial etiology or systemic infection [4]
- Signs of severe dehydration: altered mental status, syncope, oliguria, sunken eyes, poor skin turgor [4][6]
- Severe abdominal pain or peritoneal signs (especially age >50) → workup for surgical abdomen [4]
- Symptoms >7 days → consider non-viral or parasitic etiology [3]
- Immunocompromised patient → risk of severe, prolonged, or opportunistic infection (CMV, Cryptosporidium) [1]
- Extremes of age (infants <3 months, elderly ≥65) → higher risk of dehydration and complications [3][7]
3. Medications
- Oral rehydration solution (ORS): First-line therapy; low-osmolar solutions (200–250 mOsm/L) preferred [1][3]
- Ondansetron: Safe and effective for recalcitrant vomiting to facilitate oral rehydration; may be used in patients >4 years; may increase stool volume [1][7]
- Loperamide (adults only): 4 mg initial dose, then 2 mg after each unformed stool (max 8 mg/day for ≤48 hours); reduces stool frequency in acute watery diarrhea [4][8]
- Bismuth subsalicylate: Mildly effective antisecretory; safe alternative when loperamide is contraindicated [3][8]
- Loperamide + simethicone: Combination provides faster relief of diarrhea and gas-related discomfort [3]
Contraindicated/Avoid
- Loperamide in bloody/inflammatory diarrhea (risk of toxic megacolon), febrile dysentery, and children <18 years per IDSA guidelines [7]
- Loperamide contraindicated in children <2 years (respiratory depression risk) [9]
- Bismuth subsalicylate in children <12 years (Reye syndrome risk) [9]
- Antibiotics are not indicated for viral gastroenteritis [5]
4. Diet
- Early refeeding (within 4–6 hours of rehydration) shortens illness duration and improves nutritional outcomes [1][3]
- Age-appropriate regular diet is recommended; no evidence supports the traditional BRAT diet over a normal diet [3]
- Avoid: High-sugar beverages (juice, soda), caffeine, alcohol, and high-fat foods acutely, as these can worsen osmotic diarrhea
- Lactose-containing foods may transiently worsen diarrhea due to transient lactase deficiency but routine avoidance is not universally recommended
- Hydration: Frequent small sips of ORS; commercial formulations (Pedialyte 250 mOsm/L) or homemade solutions [1]
5. Review of Systems
- GI: Nausea, vomiting, diarrhea frequency/character, abdominal pain location/quality, blood in stool, tenesmus
- Constitutional: Fever, malaise, myalgias, weight loss
- Neurologic: Dizziness, lightheadedness, syncope, confusion (dehydration markers)
- Urinary: Decreased urine output, dark urine
- Cardiopulmonary: Palpitations, chest pain (electrolyte-related), dyspnea
- Skin: Rash (consider viral exanthem, reactive arthritis)
6. Collateral History and Family History
- Sick contacts: Household members, coworkers, classmates with similar symptoms — secondary attack rates are 15% for norovirus and 28% for rotavirus within households [10]
- Institutional exposure: Nursing home, daycare, cruise ship, hospital — norovirus outbreaks are common in congregate settings [5]
- Food exposure: Shared meals, restaurant visits, raw shellfish consumption
- Family history: Generally not contributory for acute viral gastroenteritis; consider IBD if recurrent episodes
- Immunocompromised household members at risk for prolonged shedding and severe disease
7. Risk Factors
- Age extremes: Children <5 years (highest incidence) and adults ≥65 years [1][11]
- Congregate living: Cruise ships, long-term care facilities, dormitories, military barracks [5]
- Foodborne exposure: Raw/undercooked shellfish, contaminated salad greens, food prepared by infected handlers [1]
- Contaminated water or inadequately treated drinking water [1]
- Seasonality: Peak in winter months in temperate climates ("winter vomiting disease") [1]
- Immunosuppression: HIV/AIDS, transplant recipients, chemotherapy — risk of prolonged/severe illness [1]
- Lack of rotavirus vaccination in children [7]
- Fomite exposure: Norovirus persists on environmental surfaces and can cause recurrent outbreaks [5]
8. Differential Diagnosis
Cannot-miss diagnoses
- Appendicitis / surgical abdomen — focal RLQ pain, peritoneal signs, fever
- Mesenteric ischemia — severe pain out of proportion to exam, age >50, atrial fibrillation
- Bowel obstruction — distension, obstipation, bilious vomiting
- Diabetic ketoacidosis — nausea/vomiting with hyperglycemia, Kussmaul breathing
- Hemolytic uremic syndrome — bloody diarrhea followed by AKI, thrombocytopenia (post-STEC)
Important alternative diagnoses
- Bacterial gastroenteritis (Salmonella, Campylobacter, Shigella, STEC) — fever, bloody/mucoid stool, more severe abdominal pain [3]
- C. difficile — recent antibiotics or hospitalization [12]
- Preformed toxin food poisoning (S. aureus, B. cereus) — onset <6 hours after suspect meal [1]
- Parasitic infection (Giardia, Cryptosporidium) — prolonged watery diarrhea, travel history [1]
- Medication-induced diarrhea — antibiotics, PPIs, metformin, colchicine, SSRIs
- Early IBD flare — recurrent episodes, weight loss, extraintestinal manifestations [3]
- Hepatitis A/E — nausea, vomiting, jaundice, transaminase elevation [1]
9. Past Medical History
- Prior episodes of gastroenteritis and their frequency
- Immunocompromising conditions: HIV, transplant, chemotherapy, biologics
- Chronic kidney disease — higher risk from dehydration and electrolyte derangements
- Cardiac disease — less tolerance for volume depletion and electrolyte shifts
- Diabetes — risk of DKA with dehydration; medication adjustments may be needed (hold metformin, SGLT2 inhibitors)
- IBD — distinguish flare from superimposed infection
- Prior abdominal surgery — adhesive obstruction can mimic gastroenteritis
- Rotavirus vaccination status in children [7]
10. Physical Exam
Vital signs
- Tachycardia, orthostatic hypotension → dehydration
- Fever — low-grade is common; high/persistent fever suggests non-viral cause [1]
Focused exam
- General: Ill-appearing, listless (severe); alert and well-appearing (mild)
- Mucous membranes: Dry or tacky → dehydration
- Eyes: Sunken (especially children) [6]
- Skin turgor: Decreased; capillary refill >2 seconds in children
- Abdomen: Diffuse mild tenderness without rebound or guarding; hyperactive bowel sounds. Focal tenderness, rigidity, or peritoneal signs → surgical evaluation
- Rectal exam: Assess for occult blood if inflammatory cause suspected [4]
- Neurologic: Altered sensorium suggests severe dehydration or alternative diagnosis
Dehydration assessment scales: The Clinical Dehydration Scale (CDS) in children uses general appearance, eyes, mucous membranes, and tears to grade severity. [6][13]
11. Lab Studies
Most cases require no laboratory testing. [1][12]
When indicated (moderate-severe illness, high-risk patients):
- BMP/CMP: Electrolytes (hyponatremia, hypokalemia), BUN/Cr (pre-renal azotemia, AKI), glucose, bicarbonate [1][3]
- Expected findings: Metabolic alkalosis (predominant vomiting) or hyperchloremic non-anion gap metabolic acidosis (predominant diarrhea); elevated BUN:Cr ratio; lactic acidosis if hypovolemic [1][14]
- CBC: Leukocytosis may suggest bacterial etiology; thrombocytopenia raises concern for HUS [7]
- Lactate: If concern for sepsis or significant hypovolemia
Stool testing — reserve for
- Bloody, mucoid, or febrile diarrhea
- Immunocompromised patients
- Symptoms ≥7 days
- Suspected outbreak (food handlers, institutional settings)
- Infants <3 months [1][3][12]
- Multiplex PCR (e.g., BioFire FilmArray GI Panel) is preferred over culture when testing is indicated [3][15]
12. Imaging
- Imaging is generally unnecessary for uncomplicated viral gastroenteritis
- Abdominal X-ray or CT abdomen/pelvis if concern for obstruction, perforation, appendicitis, or ischemia
- CT with IV contrast is the study of choice when surgical pathology is suspected
- Ultrasound may be useful in pediatric patients to evaluate for appendicitis or intussusception
13. Special Tests
- Clinical Dehydration Scale (CDS): Validated 4-item tool for children (general appearance, eyes, mucous membranes, tears) — scores 0 (none), 1–4 (some), 5–8 (moderate-severe) [13]
- Point-of-care ultrasound (POCUS): IVC collapsibility for volume assessment in adults
- Stool multiplex PCR panels: Detect 22 pathogens (bacterial, viral, parasitic) with results in ~60 minutes; useful for outbreak investigation and infection control [16]
- Rapid norovirus PCR (e.g., Xpert Norovirus): Sensitivity 92–100%, specificity 93–100%, results in 90 minutes [1]
14. ECG
- Not routinely indicated for uncomplicated viral gastroenteritis
- Obtain ECG when:
- Severe dehydration with electrolyte abnormalities suspected
- Elderly patients or those with cardiac comorbidities
- Palpitations, chest pain, or syncope
- Findings to recognize:
- Hypokalemia: Flattened T waves, U waves, ST depression, prolonged QT, risk of torsades de pointes [17]
- Hyperkalemia (less common): Peaked T waves, widened QRS, sine wave pattern [17]
- Hypomagnesemia: Prolonged QT, torsades de pointes [17]
- Sinus tachycardia from dehydration/hypovolemia
15. Assessment
Viral gastroenteritis presents as acute-onset watery, non-bloody diarrhea with nausea/vomiting, typically self-limited within 1–3 days. [1] Norovirus is the most common cause in all age groups in the post-rotavirus vaccine era, responsible for ~18% of global acute gastroenteritis cases. [1][5] Globally, rotavirus remains the leading cause of diarrheal deaths, followed by norovirus. [18]
Severity stratification
- Mild: Tolerating oral fluids, no dehydration signs, <6 stools/day
- Moderate: Some dehydration, frequent vomiting limiting oral intake, 6–10 stools/day
- Severe: Signs of significant dehydration or shock, inability to tolerate oral fluids, altered mental status
Complications: Dehydration (most common), electrolyte disturbances (hyponatremia in 16% of hospitalized children with moderate-severe dehydration), AKI, metabolic acidosis, and rarely seizures in children. [6][19]
16. Treatment Plan
Initial stabilization
Rehydration strategy by severity: [1]
- Minimal/no dehydration: Ad lib oral fluids; ORS as tolerated; half-strength apple juice is acceptable in children with mild illness [13]
- Mild-moderate dehydration: ORS 50–100 mL/kg over 3–4 hours; frequent small sips; reassess frequently
- Severe dehydration/shock: IV isotonic crystalloid (NS or LR) bolus 20 mL/kg; transition to oral rehydration once stabilized [6]
Pharmacotherapy (adults)
- Ondansetron 4–8 mg PO/IV/ODT for vomiting (facilitates oral rehydration)
- Loperamide 4 mg initially, then 2 mg after each unformed stool (max 8 mg/day × 48 hours) for watery diarrhea only [4]
- Bismuth subsalicylate 525 mg PO q30–60 min (max 8 doses/24 hours) as alternative [8]
Pharmacotherapy (children)
- Ondansetron ODT 0.15 mg/kg (max 4 mg) × 1 dose to facilitate oral rehydration in children >4 years [1][7]
- Avoid loperamide in children <18 years per IDSA [7]
- Zinc supplementation recommended in low-income settings [20]
Refeeding: Resume age-appropriate regular diet within 4–6 hours of rehydration. [1][3]
17. Disposition
Discharge criteria
- Tolerating oral fluids without recurrent vomiting
- Adequate urine output
- No signs of significant dehydration
- Reliable follow-up and ability to return if worsening
- Caregiver able to monitor (pediatric patients)
Admission criteria
- Severe dehydration unresponsive to oral/IV rehydration in ED
- Inability to tolerate oral fluids despite antiemetics
- Hemodynamic instability or signs of shock
- Significant electrolyte abnormalities requiring correction
- Infants <3 months with dehydration
- Immunocompromised with severe symptoms
- Concern for alternative surgical diagnosis
Observation: Consider for patients with moderate dehydration requiring IV fluids who may improve with a few hours of rehydration and reassessment. [13]
Specialist consultation
- Surgery if peritoneal signs or concern for surgical abdomen
- GI if prolonged symptoms (>7 days), suspected IBD, or immunocompromised with refractory disease
- Infectious disease for immunocompromised patients with severe or prolonged illness
18. Follow Up / Return Precautions
Follow-up timing
- Most patients recover within 1–3 days [1]
- PCP follow-up in 2–3 days if symptoms persist; sooner for high-risk patients (elderly, infants, immunocompromised)
Return precautions — instruct patients to return immediately for:
- Inability to keep down any fluids for >12–24 hours
- Bloody or black stools
- High fever (>101.3°F / 38.5°C)
- Severe abdominal pain or distension
- Decreased urination, no tears (children), dizziness/lightheadedness
- Confusion or lethargy
- Symptoms worsening after initial improvement or lasting >7 days
Patient counseling
- Hand hygiene is the most effective prevention measure; alcohol-based sanitizers have limited efficacy against norovirus (soap and water preferred) [5]
- Contagion period: Patients remain infectious for ≥48 hours after symptom resolution; food handlers should not return to work until 48 hours symptom-free [5]
- Environmental decontamination: Norovirus persists on surfaces; clean with bleach-based solutions [5]
- Rotavirus vaccination for eligible infants [7]
The following algorithm from the AAFP provides a practical framework for evaluating and managing acute diarrhea in the ED and primary care settings:
References
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