About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Age drives management: neonates and infants ≤90 days with rectal temperature ≥38.0°C need structured assessment for invasive bacterial infection even if well appearing
- Toxic appearance, lethargy, poor perfusion, respiratory distress, petechiae/purpura, bulging fontanelle, or non-blanching rash are emergency red flags
- Urinary tract infection is the most common serious bacterial infection in young febrile children without a source
- Do not rely on fever height alone — clinical appearance, age, hydration, immunization status, and source are more important
- In older immunized children who are well appearing, management is usually source-directed with safety-netting rather than broad invasive testing
Approach to the Presentation
Fever in a child is not a diagnosis; it is a risk-stratification problem. First decide whether the child is critically ill, then stratify by age: neonate, young infant, toddler, and older child. Rectal temperature ≥38.0°C is clinically significant in infants ≤90 days. In this group, even well-appearing infants may have urinary tract infection, bacteremia, or meningitis and should be assessed using Canadian Paediatric Society guidance and local pathways. In children older than 3 months, the focus shifts to appearance, hydration, immunization status, focal symptoms, and red flags.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Sepsis / Invasive Bacterial Infection | must-not-miss | Toxic appearance, poor perfusion, lethargy, temperature instability, tachycardia out of proportion, mottling | Blood culture, CBC, inflammatory markers, lactate, urinalysis/culture, CSF studies when indicated |
| Meningitis | must-not-miss | Fever with irritability, lethargy, bulging fontanelle, poor feeding, vomiting, seizures, neck stiffness | Lumbar puncture with CSF cell count, glucose, protein, Gram stain/culture |
| Urinary Tract Infection / Pyelonephritis | must-not-miss | Fever without source, vomiting, poor feeding, abdominal pain, dysuria, frequency, foul-smelling urine | Urinalysis and urine culture from catheter specimen or clean-catch |
| Pneumonia | must-not-miss | Fever with tachypnea, cough, increased work of breathing, hypoxia, focal crackles, reduced air entry | Clinical diagnosis supported by CXR if severe, hypoxic, uncertain, or complications suspected |
| Meningococcemia | must-not-miss | Fever with non-blanching petechiae/purpura, toxic appearance, leg pain, cold extremities, shock | Clinical emergency — blood culture if feasible but do not delay ceftriaxone/cefotaxime |
| Viral URI | common | Rhinorrhea, cough, sore throat, low-grade fever, well appearing, normal perfusion | Clinical diagnosis |
| Acute Otitis Media | common | Fever with ear pain, irritability, sleep disturbance, bulging erythematous tympanic membrane | Otoscopy showing middle-ear effusion and acute inflammation |
| Gastroenteritis | common | Fever with vomiting and/or diarrhea, crampy abdominal pain, exposure history | Clinical diagnosis; stool testing only for red flags |
| Kawasaki Disease | less common | Fever ≥5 days plus conjunctivitis, mucous membrane changes, extremity changes, rash, cervical lymphadenopathy | Clinical criteria, inflammatory markers, echocardiography |
| Malignancy / Leukaemia | rare | Persistent or recurrent fever, pallor, bruising, petechiae, bone pain, lymphadenopathy, hepatosplenomegaly | CBC with differential, smear, LDH/uric acid |
Red Flags & Key History
Symptoms
Age ≤90 days with rectal temperature ≥38.0°C
Poor feeding, lethargy, inconsolability, weak cry, decreased responsiveness
Non-blanching rash, petechiae, purpura, leg pain, cold hands/feet
Respiratory distress, grunting, cyanosis, apnoea, or hypoxia
Seizure, bulging fontanelle, persistent vomiting, neck stiffness, or photophobia
Incomplete immunizations or immunocompromised state
Fever ≥5 days with conjunctivitis, rash, red lips/tongue, swollen hands/feet
Rhinorrhea, mild cough, preserved hydration, normal activity between fever spikes
Signs
Toxic appearance, altered level of consciousness, weak cry, hypotonia
Delayed capillary refill, mottling, tachycardia out of proportion, hypotension
Bulging fontanelle or meningism
Tachypnea, recession, grunting, focal crackles, low oxygen saturation
Dehydration: dry mucosa, absent tears, sunken eyes/fontanelle, reduced urine output
Bulging tympanic membrane with effusion
Approach to Investigation
First-line
Vitals and appearance assessmentTemperature route, HR, RR, BP when appropriate, oxygen saturation, capillary refill, hydration status, mental status
Urinalysis and urine cultureHigh-yield in febrile infants and young children without source
CBC, blood culture, inflammatory markersFor infants ≤90 days by age/risk pathway, ill-appearing children, suspected sepsis, or unclear source with concerning features
Point-of-care glucoseIf altered mental status, poor intake, seizure, or toxic appearance
Second-line
Lumbar punctureFor ill-appearing infants/children, suspected meningitis, and many neonates/young infants depending on age and inflammatory markers
Chest X-rayIf hypoxia, significant respiratory distress, focal signs, prolonged fever with cough, or unclear source
Respiratory viral testingWhen it changes isolation, antiviral decisions, cohorting, or admission planning
Electrolytes, creatinine, lactate, blood gasIf dehydrated, septic, poor perfusion, persistent vomiting, or requiring IV fluids
Specialist
EchocardiographyIf Kawasaki disease or MIS-C is suspected
Paediatric consultationFor febrile neonates, toxic children, immunocompromised patients, meningitis, sepsis, complicated pneumonia, or persistent fever without source
Management Principles
Canadian Paediatric Society febrile infant guidance and PHAC/NACI immunization context1
Immediate stabilization
- ABCs, oxygen if hypoxic, IV/IO access if unstable, glucose check, fluid resuscitation for shock
- If sepsis or meningitis suspected: obtain cultures if feasible but do not delay empiric antibiotics
- Use age-appropriate empiric antibiotics according to local pathway and resistance patterns
2
Neonates and young infants
- Rectal temperature ≥38.0°C in infants ≤90 days requires structured assessment even if well appearing
- Risk-stratify using age bands, urinalysis, inflammatory markers, and CSF assessment when indicated
- Admit most neonates and any ill-appearing infant; outpatient management only for carefully selected low-risk infants with reliable follow-up
3
Older infants and children
- If well appearing and immunized with a clear viral source: supportive care, antipyretics for comfort, hydration advice, and safety-netting
- Treat focal bacterial infection when identified
- Assess hydration and urine output before discharge
Complications & Pitfalls
- Under-triaging the young febrile infant: a smiling infant under 90 days can still have bacteremia, meningitis, or UTI.
- False reassurance from a viral result: viral positivity reduces but does not eliminate bacterial infection risk.
- Using bag urine cultures diagnostically: contamination can cause unnecessary antibiotics and admissions.
- Missing Kawasaki disease: fever for 5 days with mucocutaneous features warrants inflammatory markers and echocardiography consideration.
MCCQE1 Exam Tips
- 1First sort by age: neonate/young infant versus older child
- 2Rectal temperature ≥38.0°C in an infant ≤90 days is clinically important even if measured at home
- 3Fever without source in a young child: UTI is the common serious bacterial infection
- 4Non-blanching petechiae or purpura with fever is meningococcemia until proven otherwise
- 5Do not choose CT head for simple fever unless focal neurological signs, trauma, or prolonged altered mental status are present
- 6Well-appearing older immunized child with viral URI features usually needs supportive care and safety-netting
- 7CanMEDS communication: parents need clear red flags and return precautions
practicetest your knowledge on fever in a childApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — paediatric and beyond.
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