What are the appropriate management and differential diagnoses for a child under 5 presenting with persistent fever for up to a week, worsening diarrhea, and leukocytosis?

Management and Differential Diagnosis for Child Under 5 with Persistent Fever, Worsening Diarrhea, and Leukocytosis

This child requires immediate antibiotic therapy given the combination of fever persisting up to a week, worsening diarrhea, and leukocytosis (WBC 25,000), which strongly suggests bacterial enteritis requiring specific antimicrobial treatment. 1

Immediate Assessment and Risk Stratification

Assess hydration status first - this determines whether the child needs IV fluids or can tolerate oral rehydration:

• Mild dehydration (3-5% deficit): increased thirst, slightly dry mucous membranes 1
• Moderate dehydration (6-9% deficit): loss of skin turgor, skin tenting when pinched, dry mucous membranes 1
• Severe dehydration (≥10% deficit): severe lethargy, prolonged skin tenting >2 seconds, cool extremities, decreased capillary refill, rapid deep breathing (acidosis) 1

Key clinical features to document:

• Presence of blood or mucus in stool (dysentery) 1
• Fever documented in medical setting 1
• Signs of sepsis or altered mental status 1
• Abdominal pain, tenesmus, frequency of bloody stools 1

Critical Differential Diagnoses

Given the presentation of prolonged fever (up to 1 week), worsening diarrhea, and marked leukocytosis, prioritize these bacterial causes:

Primary considerations:

• Shigella - presents with bacillary dysentery (frequent scant bloody stools, fever, abdominal cramps, tenesmus) 1
• Salmonella - can cause prolonged fever with enteritis and bacteremia in young children 1
• Campylobacter - bloody diarrhea with fever 1
• Enteropathogenic E. coli - watery diarrhea that can worsen over days 1

Important to exclude:

• STEC (Shiga toxin-producing E. coli) - critical because antibiotics are contraindicated and can precipitate hemolytic uremic syndrome 1
• Urinary tract infection - causes >90% of serious bacterial illness in children under 5 and can present with fever and nonspecific symptoms 2

Immediate Management Algorithm

1. Rehydration Based on Dehydration Status

For mild-moderate dehydration:

• Oral rehydration solution (ORS) with 50-90 mEq/L sodium 1
• 50 mL/kg over 2-4 hours for mild dehydration 1
• 100 mL/kg over 2-4 hours for moderate dehydration 1
• Small frequent volumes initially (5 mL every minute via spoon or syringe) 1

For severe dehydration:

• Immediate IV rehydration with Ringer's lactate or normal saline 1
• Boluses of 20 mL/kg until pulse, perfusion, and mental status normalize 1
• May require two IV lines or alternate access (venous cutdown, femoral vein, intraosseous) 1
• Once conscious, can complete remaining deficit with ORS 1

2. Diagnostic Testing

Obtain immediately:

• Stool culture - indicated for dysentery (bloody diarrhea) 1
• Blood culture - given high fever and leukocytosis suggesting possible bacteremia 1
• Urinalysis and urine culture - UTI is the most common serious bacterial infection in this age group 2
• Stool microscopy if available 1

Consider serum electrolytes if clinical signs suggest abnormal sodium or potassium concentrations 1

3. Antibiotic Therapy

Empiric antibiotics are indicated NOW because this child meets multiple criteria: 1

• High fever present
• Watery diarrhea lasting >5 days (approaching 1 week)
• Worsening clinical course
• Marked leukocytosis (WBC 25,000)

Empiric antibiotic choice for children:

• Azithromycin (preferred for most bacterial enteritis including Shigella, Campylobacter, Salmonella) 1
• Third-generation cephalosporin if child appears septic or has neurologic involvement 1
• Adjust based on local susceptibility patterns 1

Critical caveat: If STEC is suspected (particularly bloody diarrhea), avoid antibiotics as they increase risk of hemolytic uremic syndrome 1. However, given worsening diarrhea and high fever, bacterial dysentery is more likely than STEC.

4. Nutritional Management

Continue feeding immediately upon rehydration: 1

• Breast-fed infants: continue nursing on demand 1
• Formula-fed infants: full-strength lactose-free or lactose-reduced formula preferred; if unavailable, use full-strength lactose-containing formula under supervision 1
• Older children: age-appropriate usual diet with starches, cereals, yogurt, fruits, vegetables 1
• Avoid: foods high in simple sugars and fats 1

Replace ongoing losses: 10 mL/kg ORS for each watery stool, 2 mL/kg for each vomiting episode 1

5. Adjunctive Therapy

Antiemetics if needed:

• Ondansetron may be given to children >4 years to facilitate oral rehydration if vomiting is prominent 1

Avoid antimotility agents:

• Never use loperamide in children <18 years 1
• Antimotility drugs contraindicated with fever or bloody diarrhea due to risk of toxic megacolon 1

Common Pitfalls to Avoid

Do not delay antibiotics - the combination of prolonged fever (up to 1 week), worsening diarrhea, and leukocytosis mandates empiric treatment while awaiting cultures 1

Do not withhold feeding - early refeeding reduces duration of diarrhea and prevents malnutrition 1

Do not use antibiotics if STEC confirmed - wait for stool culture results if bloody diarrhea without high fever, as antibiotics worsen outcomes with STEC O157 and Shiga toxin 2-producing strains 1

Do not rely on stool pH or reducing substances alone - these do not diagnose lactose intolerance without clinical worsening of diarrhea 1

Disposition and Follow-up

Admit to hospital if:

• Severe dehydration requiring IV fluids 1
• Failed oral rehydration therapy 1
• Altered mental status 1
• Signs of sepsis 1
• Age <3 months with suspected bacterial infection 1

Discharge with close follow-up if:

• Successfully rehydrated with ORS 1
• Tolerating oral intake 1
• Reliable caregiver who can monitor and return if worsening 1
• Empiric antibiotics started 1

Instruct parents to return immediately if: child becomes irritable or lethargic, has decreased urine output, develops intractable vomiting, or diarrhea persists beyond antibiotic course 1