How to differentiate between infectious and non-infectious elbow bursitis?

Differentiating Between Infectious and Non-Infectious Elbow Bursitis

The most effective way to differentiate between infectious and non-infectious elbow bursitis is through bursal aspiration with fluid analysis including Gram stain, culture, cell count, crystal analysis, and glucose measurement. 1, 2

Clinical Evaluation

History and Physical Examination

• Infectious (septic) bursitis typically presents with more pronounced erythema, warmth, and tenderness compared to non-infectious bursitis 1
• Presence of fever, chills, or systemic symptoms suggests infectious etiology 2
• Recent trauma, puncture wound, or abrasion increases risk of infection 3
• Chronic microtrauma (occupational or recreational activities requiring repetitive pressure on the elbow) often leads to non-infectious bursitis 2
• Underlying conditions like gout, rheumatoid arthritis, or immunosuppression may predispose to either type but should raise suspicion for infection in immunocompromised patients 4, 2

Imaging Studies

• Initial radiographs should be obtained to exclude fractures and assess for soft tissue swelling or gas 5
• Ultrasound is highly useful for distinguishing bursitis from cellulitis and can detect bursal fluid collections, synovial thickening, and surrounding soft tissue changes 5
• MRI with contrast can help evaluate the extent of infection, detect abscesses, and assess for osteomyelitis in cases where infection is suspected to extend beyond the bursa 5

Bursal Fluid Analysis

• Aspiration of bursal fluid is the gold standard for differentiation 1, 2

• Infectious bursitis typically shows:

  • Cloudy or purulent fluid appearance 3
  • WBC count >3,000/mm³ (often >10,000/mm³) with neutrophil predominance 2
  • Positive Gram stain (though may be negative in up to 30% of cases) 1
  • Positive culture (Staphylococcus aureus is most common pathogen) 2
  • Low glucose compared to serum 2

• Non-infectious bursitis typically shows:

  • Clear, straw-colored fluid 3
  • WBC count <3,000/mm³ 2
  • Negative Gram stain and culture 1
  • Normal glucose levels 2
  • May contain crystals in cases of gout or pseudogout 2

Laboratory Tests

• Elevated serum WBC count and inflammatory markers (ESR, CRP) may suggest infection but are not specific 2
• Blood cultures should be considered in patients with suspected septic bursitis, especially those with systemic symptoms 2

Management Approach

• If infectious bursitis is confirmed:

  • Antibiotics effective against Staphylococcus aureus (first-line treatment) 2
  • Repeated aspiration may be necessary 1
  • Consider hospitalization and IV antibiotics for severe cases or immunocompromised patients 2
  • Surgical drainage for cases not responding to antibiotics 2

• For non-infectious bursitis:

  • Conservative management with rest, ice, compression, and elevation 6
  • NSAIDs for symptomatic relief 1
  • Aspiration for symptomatic relief (with caution due to risk of introducing infection) 6
  • Address underlying cause (modify activities, padding for chronic microtrauma) 2

Pitfalls and Caveats

• Clinical features alone cannot reliably distinguish between septic and non-infectious bursitis as local erythema may be present in both 1
• Intrabursal corticosteroid injections should be avoided if infection has not been ruled out 2
• Patients on immunosuppressive therapy are at higher risk for atypical infections, including fungal infections 4
• Chronic bursitis may require surgical intervention (bursectomy) if recurrent or refractory to conservative treatment 6
• Always perform aspiration before starting antibiotics to increase yield of cultures 1