What does the presence of air in the gluteus muscle indicate?

Air in the Gluteus Muscle: Diagnosis and Management

The presence of air in the gluteus muscle without a history of recent surgery, trauma, or puncture wound is a reliable indication of infection and should be treated as a medical emergency until proven otherwise. 1

Causes and Clinical Significance

Air in the gluteus muscle typically indicates one of the following conditions:

• Infectious causes:

  • Necrotizing fasciitis
  • Gas gangrene (clostridial myonecrosis)
  • Non-clostridial anaerobic infection
  • Polymicrobial infection with gas-forming organisms

• Non-infectious causes:

  • Recent trauma with air entry
  • Post-surgical state
  • Procedural complication (injection, biopsy)
  • Subcutaneous emphysema from adjacent structures

Diagnostic Approach

Imaging

• Plain radiographs: Well-suited for initial detection of soft tissue gas but limited for deep fascial gas evaluation 1
• CT scan: Most sensitive modality for detecting soft tissue gas; can delineate extent and compartmental location 1
  • Look for: fascial thickening, inflammatory fat stranding, fluid collections along fascial planes, and soft tissue gas 1
• MRI: Less sensitive than CT for gas detection but superior for evaluating fascial fluid and edema 1
  • Gradient-echo sequences can help identify air through susceptibility artifact 1

Laboratory Tests

• Complete blood count with differential
• C-reactive protein and erythrocyte sedimentation rate
• Blood cultures
• Tissue cultures when possible

Management Algorithm

1. Immediate assessment of hemodynamic stability

   • If unstable: Resuscitation, broad-spectrum antibiotics, and urgent surgical consultation

2. For stable patients:

   • Obtain CT scan to determine extent and location of gas
   • Evaluate for systemic signs of infection

3. Treatment based on clinical presentation:

   A. If signs of necrotizing infection (severe pain, rapid progression, systemic toxicity):

   • Immediate surgical exploration and debridement 1
   • Broad-spectrum antibiotics covering aerobic and anaerobic organisms
   • Consider hyperbaric oxygen therapy as adjunctive treatment 2

   B. If localized infection without systemic toxicity:

   • Targeted antibiotics based on likely pathogens
   • Close monitoring for progression
   • Surgical drainage if abscess is present
   • For abscesses larger than 4 cm, consider percutaneous drainage 1

   C. If post-procedural or post-traumatic without infection:

   • Close observation
   • Prophylactic antibiotics if high risk for infection

Important Considerations

• Time is critical: Mortality from necrotizing soft tissue infections increases with delayed diagnosis and treatment 2, 3
• Diagnostic pitfall: The absence of crepitus or visible skin changes does not exclude serious infection; deep infections may not manifest superficially until advanced stages
• Immunocompromised patients: Lower threshold for aggressive intervention as they may present with atypical or minimal symptoms despite severe infection 3
• Polymicrobial nature: Gas-forming infections often involve multiple organisms including anaerobes, requiring broad antimicrobial coverage 4

Prognosis

Prognosis depends on:

• Speed of diagnosis and intervention
• Extent of infection
• Patient's comorbidities
• Causative organisms

Without proper treatment, gas gangrene and necrotizing fasciitis have mortality rates of up to 30-80% 2, 5. With early aggressive surgical debridement, appropriate antibiotics, and supportive care, survival rates have improved significantly.