What are we looking for in a chest x-ray (CXR) as a septic screen?

What to Look for in Chest X-ray as a Septic Screen

When performing a chest X-ray as part of a septic screen, we are primarily looking for evidence of pneumonia, which is the most commonly identified source of infection in the chest, occurring in 38.6% of patients with sepsis. 1

Primary Findings to Identify

• Consolidation patterns: Air-space opacities limited to one lobe or segment (typical of community-acquired pneumonia)
• Infiltrates: Patchy or diffuse opacities that may indicate infection
• Pleural effusions: Fluid collections that may represent parapneumonic effusions or empyema
• Multiple peripheral nodules: May indicate septic emboli
• Cavitation: Areas of necrosis within consolidations suggesting abscess formation

Limitations of Chest X-ray in Sepsis

• Chest radiography has limited sensitivity (58%) but good specificity (91%) for diagnosing pneumonia in septic patients 1
• Normal chest X-ray does not rule out pneumonia or other pulmonary sources of infection
• Early pneumonic changes may not be visible on initial chest X-ray

Additional Considerations During Interpretation

• Device placement: Evaluate proper positioning of endotracheal tubes and central venous catheters, which can be sources of infection 1
• Bilateral multicentric opacities: May suggest aspiration pneumonia
• Diffuse multifocal involvement: Common in nosocomial pneumonia, especially in ICU patients

When to Escalate to Advanced Imaging

• CT chest with IV contrast is recommended if:

  • Initial chest X-ray is normal, equivocal, or nonspecific but clinical suspicion remains high
  • Patient is not improving clinically despite appropriate therapy
  • Complications are suspected (abscess, empyema)

• CT has a much higher diagnostic yield with a positive predictive value of 81.82% for identifying septic foci 1, 2

• CT can detect septic foci in 76.5% of cases in emergency department patients with suspected sepsis 1

Practical Approach to Chest X-ray in Sepsis

1. Systematic evaluation: Assess all lung zones, pleural spaces, mediastinum, and bony structures
2. Compare with prior imaging: Look for new or evolving abnormalities
3. Correlate with clinical findings: Respiratory symptoms, vital signs, and laboratory markers
4. Document placement of lines/tubes: Ensure they are not potential sources of infection

Common Pitfalls

• Relying solely on chest X-ray to rule out pulmonary infection in sepsis
• Failing to recognize subtle findings that may indicate early infection
• Not considering CT chest when chest X-ray is negative but clinical suspicion remains high
• Delaying antimicrobial therapy while waiting for imaging results 2

Remember that while chest X-ray is a valuable initial screening tool for sepsis evaluation due to its portability and rapid acquisition, its limitations must be recognized, and further imaging with CT should be pursued when clinical suspicion remains high despite negative or equivocal chest X-ray findings.