Evaluation and Management of Fever with Leg Pain
A patient presenting with fever and leg pain requires immediate assessment for serious bacterial infections including osteomyelitis, septic arthritis, intramuscular abscess, and psoas abscess, with inability to bear weight being a critical red flag for bacterial infection.
Initial Clinical Assessment
Key Historical and Physical Examination Findings
Inability to bear weight on the affected limb strongly predicts bacterial infection (osteomyelitis, septic arthritis, or intramuscular abscess) and mandates aggressive workup 1
Assess for psoas abscess by testing painful passive hip extension, endorotation, and flexion stress-test of the hip joint 2
Evaluate for skin and soft tissue involvement including erythematous maculopapular lesions, focal cellulitis, cutaneous nodules, or ecthyma gangrenosum, particularly in immunocompromised patients 3
Document fever pattern, duration of symptoms, and any recent trauma or exposures 4
Diagnostic Workup
Essential Laboratory Studies
Complete blood count with differential to assess for leukocytosis and neutropenia 1, 5
Erythrocyte sedimentation rate (ESR) >36 mm/hour and C-reactive protein (CRP) >60 mg/L are highly associated with osteomyelitis or septic arthritis 1
Blood cultures before initiating antibiotics if septic shock is present or if results will change management 6
Imaging Strategy
Ultrasound should be performed first if psoas abscess is suspected; if inconclusive, proceed to CT scan 2
MRI is the most useful imaging modality for definitive diagnosis of musculoskeletal infections, particularly in patients with multiple visits or unclear diagnosis (ordered in 63% of children with multiple visits vs 34% with single visit) 1
Consider aspiration and/or biopsy of affected tissues for cytological/histological assessment, microbial staining, and cultures to establish definitive diagnosis 3
Management Approach
For Immunocompetent Patients with Suspected Bacterial Infection
Initiate empiric antibiotics targeting the most likely pathogens based on clinical presentation 4
For confirmed osteomyelitis or septic arthritis, treat for 7-14 days based on antimicrobial susceptibilities 3
Percutaneous or surgical drainage is required for psoas abscess combined with antibiotic therapy 2
For Neutropenic Patients (High-Risk Population)
Immediate hospitalization with empiric vancomycin PLUS antipseudomonal antibiotics (cefepime, carbapenem [imipenem-cilastatin, meropenem, or doripenem], or piperacillin-tazobactam) is mandatory 3
Aggressively pursue tissue diagnosis through aspiration/biopsy of skin and soft tissue lesions for comprehensive microbiologic evaluation 3
Surgical intervention is indicated for soft tissue abscess drainage after marrow recovery or for progressive polymicrobial necrotizing fasciitis or myonecrosis 3
For Persistent or Recurrent Fever in Neutropenic Patients
Add empiric antifungal therapy (yeasts and molds are primary causes) if fever persists beyond 4-7 days 3
Escalate to vancomycin or other gram-positive coverage (linezolid, daptomycin, or ceftaroline) if not already administered 3
Critical Pitfalls to Avoid
Do not rely solely on oral temperatures—core temperatures should be utilized if fever is suspected, as oral measurements have poor sensitivity 6
Fever may be absent in elderly and immunocompromised patients despite true infection 6
The initial ED diagnosis is correct only 42% of the time in pediatric fever with extremity pain, emphasizing the need for comprehensive laboratory and imaging evaluation 1
Do not delay imaging in patients unable to bear weight or with significantly elevated inflammatory markers (ESR >36, CRP >60) 1
Consider non-infectious causes of fever and leg pain including inflammatory conditions, though infectious etiologies must be ruled out first 4, 6