Radiographic Features of Bronchopneumonia and Lobar Pneumonia
Bronchopneumonia (Lobular Pattern)
Bronchopneumonia presents as multifocal, patchy airspace opacities that are typically bilateral and scattered, affecting multiple lobes in a non-segmental distribution.
Key Radiographic Features:
- Patchy, multifocal consolidations scattered throughout both lungs
- Peribronchial distribution with involvement centered around airways
- Multiple small opacities rather than homogeneous lobar consolidation
- Bilateral involvement is common
- Lower lung zone predominance typical but not exclusive
- May show air bronchograms within areas of consolidation
- Often accompanied by ill-defined centrilobular nodules
Top 3 Differentials for Bronchopneumonia Pattern:
Aspiration pneumonia - Look for dependent distribution (posterior segments of upper lobes or superior segments of lower lobes), history of dysphagia, altered consciousness, or witnessed aspiration event 1
Organizing pneumonia (OP) - Demonstrates multifocal patchy alveolar opacities with peribronchovascular and/or peripheral distribution, may show reversed halo sign, often migrates on serial imaging 1
Hypersensitivity pneumonitis - Shows poorly defined small centrilobular nodules, bilateral ground-glass opacities, mosaic attenuation pattern (three-density pattern), and air trapping on expiratory images 2, 1
Lobar Pneumonia
Lobar pneumonia manifests as homogeneous consolidation confined to one or more complete lobes with sharp demarcation at fissure boundaries, classically caused by Streptococcus pneumoniae.
Key Radiographic Features:
- Homogeneous, dense consolidation involving an entire lobe
- Sharp borders at interlobar fissures (fissure sign)
- Air bronchograms prominently visible throughout the consolidated lobe
- Segmental or lobar distribution respecting anatomic boundaries
- Usually unilateral, though can be bilateral
- Volume loss is typically absent or minimal (distinguishes from atelectasis)
- May progress through stages: congestion → red hepatization → gray hepatization (though these stages don't necessarily occur sequentially) 3
Top 3 Differentials for Lobar Pneumonia Pattern:
Pulmonary edema (hydrostatic or permeability) - Bilateral symmetric distribution, basal predominance, Kerley B lines, peribronchial cuffing, pleural effusions more common in hydrostatic type; clinical context of heart failure or ARDS crucial 1
Pulmonary hemorrhage - May present with consolidation, but look for hemoptysis, anemia, hemosiderin-laden macrophages if bronchoscopy performed; often associated with vasculitis or coagulopathy 1
Acute interstitial pneumonia (AIP/DAD pattern) - Extensive bilateral ground-glass opacities and dependent airspace consolidation, predominantly subpleural distribution, rapid progression to respiratory failure, mimics ARDS radiographically 4
Critical Clinical Pearls:
Important caveat: The classic teaching that lobar pneumonia equals pneumococcal infection is outdated. Studies show that 61% of hospitalized pneumococcal pneumonia patients actually present with a bronchopneumonic pattern rather than lobar consolidation 5. The bronchopneumonic pattern is associated with underlying malignancy and lower bacteremia rates (9% vs 54% for lobar pattern) 5.
Pattern overlap is common: Many pneumonias demonstrate mixed patterns, and the radiographic appearance alone cannot definitively identify the causative organism 6, 7. Clinical context, epidemiologic factors, and laboratory data must guide diagnosis.
Viral pneumonias typically show an airway-centric bronchopneumonia pattern; the presence of lobar consolidation in viral infections usually suggests bacterial coinfection (except adenovirus) 8.
Time-sensitive consideration: While chest radiography remains the standard initial imaging modality, CT is superior for detecting complications (abscess, empyema), evaluating treatment-refractory cases, and assessing immunocompromised patients 9, 10.