What is the appropriate evaluation and management for a patient presenting with acute nausea, vomiting, diarrhea, and fever?

Acute Nausea, Vomiting, Diarrhea with Fever: Evaluation and Management

In an immunocompetent adult presenting with acute nausea, vomiting, diarrhea, and fever, the most likely diagnosis is viral gastroenteritis (particularly norovirus), and the cornerstone of management is aggressive oral rehydration with ORS—empiric antibiotics are not indicated unless specific red flags are present. 1

Initial Clinical Assessment

Assess dehydration severity immediately by examining:

• Skin turgor and mucous membrane moisture 1
• Mental status changes 1
• Tachycardia with orthostatic vital signs 1
• Capillary refill time 1
• Urine output 2

Document stool characteristics:

• Frequency and volume 3
• Presence of blood, mucus, or pus 3
• Watery versus bloody appearance 3

Identify red-flag features requiring further investigation:

• High fever >38.5°C 1, 2
• Severe abdominal pain 1
• Bloody diarrhea with systemic toxicity 3, 1
• Symptoms persisting >3 days 1
• Signs of severe dehydration (hypotension, oliguria, altered mental status) 2
• Immunocompromised status 3

Obtain epidemiological history:

• Recent international travel 3, 2
• Recent antibiotic use (raises concern for C. difficile) 3
• Food exposures and sick contacts 3
• Day-care or long-term care facility exposure 3

Rehydration Strategy (Highest Priority)

For mild-to-moderate dehydration:

• Administer reduced-osmolarity ORS at 50–100 mL/kg over 3–4 hours 1
• Adults (≥30 kg) should receive 2–4 L of ORS during initial rehydration 1
• Replace ongoing losses with 120–240 mL of ORS per diarrheal stool or vomiting episode, up to approximately 2 L per day 1

For severe dehydration or inability to tolerate oral intake:

• Initiate intravenous isotonic fluids (lactated Ringer's or normal saline) 1
• Consider nasogastric ORS administration if oral intake is not tolerated but dehydration is not severe 1

Antiemetic Therapy

Ondansetron 4–8 mg orally every 8 hours as needed can be used to control significant vomiting and facilitate oral rehydration 1. This approach is supported by evidence showing ondansetron reduces vomiting rates, improves oral rehydration tolerance, and decreases need for IV rehydration 4, 5.

Important ondansetron precautions:

• Avoid in patients with congenital long QT syndrome 6
• Monitor ECG in patients with electrolyte abnormalities (hypokalemia, hypomagnesemia), congestive heart failure, or bradyarrhythmias 6
• Use caution with concomitant serotonergic drugs due to serotonin syndrome risk 6

Antimotility Agents

Loperamide should be avoided until a viral cause is confirmed and inflammatory etiologies are excluded 1. It is contraindicated in children <18 years 1.

Critical loperamide contraindications:

• High fever ≥38.5°C 2
• Bloody diarrhea 7
• Suspected invasive bacterial infection 2
• Risk of toxic megacolon 2

If used for confirmed watery viral diarrhea: 4 mg initially, then 2 mg after each loose stool (maximum 16 mg/day) 1, 7.

Antibiotic Decision Algorithm

Empiric antibiotics are NOT recommended for acute watery diarrhea in immunocompetent adults without recent international travel 1. The evidence shows antibiotics shorten illness by only ~1 day on average, which does not outweigh the risks of resistance, adverse effects, and potential harm in certain infections 1.

Consider empiric antibiotics ONLY in these specific situations:

1. High fever >38.5°C with bloody diarrhea and systemic toxicity (suggesting invasive bacterial infection like Shigella) 3, 2
2. Recent international travel with fever ≥38.5°C or signs of sepsis 3
3. Immunocompromised patients with severe illness 3
4. Infants <3 months of age with suspected bacterial etiology 3
5. Bacillary dysentery presentation (frequent scant bloody stools, fever, abdominal cramps, tenesmus) 3

Empiric antibiotic choices:

• Azithromycin (preferred in areas with fluoroquinolone resistance) 3, 2
• Ciprofloxacin (based on local susceptibility patterns) 3, 2

Stop antibiotics immediately if viral cause is confirmed 1.

Diagnostic Testing Indications

Obtain stool testing (culture, leukocytes, C. difficile toxin) when:

• Symptoms persist >48 hours 2
• Clinical deterioration occurs 2
• Bloody stools are present 2
• Patient is immunosuppressed 2
• Leukocytosis is present 3
• Recent antibiotic use (raises C. difficile concern) 3

During COVID-19 or similar viral outbreaks:

• Consider that acute GI symptoms may represent COVID-19 or other viral illness, which can predate respiratory symptoms 3
• GI pathogen testing including C. difficile should be considered for inpatients and outpatients with ongoing symptoms 3

Nutritional Management

Resume age-appropriate diet immediately after (or during) rehydration 1. Early refeeding does not prolong diarrhea and may reduce duration by approximately half a day 8.

• Provide easily digestible foods: starches, cereals, cooked vegetables 1
• Avoid foods high in simple sugars and caffeinated beverages (worsen diarrhea via osmotic effects) 1

Critical Pitfalls to Avoid

Do not prescribe empiric antibiotics for uncomplicated acute watery diarrhea—this promotes resistance and offers minimal benefit 1, 9.

Never use antimotility agents in patients with high fever or bloody diarrhea—risk of toxic megacolon and masking clinical deterioration 2, 7.

Avoid inadequate fluid resuscitation—this is the leading cause of morbidity and mortality in acute gastroenteritis 1.

Do not use antibiotics for suspected STEC O157 or other Shiga toxin 2–producing STEC—antibiotics increase risk of hemolytic uremic syndrome 3.

Monitor QTc carefully when using ondansetron, especially with concomitant QT-prolonging medications (hydroxychloroquine, azithromycin, antiarrhythmics) 3, 6.

Indications for Hospitalization

Immediate medical evaluation or hospitalization is required for:

• Severe dehydration (hypotension, tachycardia, oliguria, altered mental status) 2
• Inability to maintain oral hydration despite antiemetics 2
• Persistent high fever despite treatment 2
• Signs of systemic illness or sepsis 3, 2
• Hemodynamic instability 10

Expected Clinical Course

Most viral gastroenteritis is self-limiting:

• Norovirus: 12–72 hours in immunocompetent hosts 1
• Rotavirus: 4–7 days 1
• Clinical improvement expected within 5–7 days with supportive therapy 2

Reassess if symptoms persist beyond expected timeframe or clinical deterioration occurs 1, 2.