## Distinguishing Lobar from Bronchopneumonia ### Pathological Definition **Key Point:** Lobar pneumonia consolidates an entire lobe in a sequential manner (red hepatization → gray hepatization → resolution), respecting anatomical boundaries. Bronchopneumonia spreads along airways without regard to lobar anatomy. ### Radiological Hallmarks | Feature | Lobar Pneumonia | Bronchopneumonia | |---------|-----------------|------------------| | **Distribution** | Entire lobe or segment; homogeneous | Patchy, multifocal; bronchocentric | | **Boundaries** | Respects lobar/segmental anatomy | Crosses lobar boundaries | | **Air bronchograms** | Present (hallmark) | May be present but less prominent | | **Lobar involvement** | Single lobe common | Multiple lobes, bilateral | | **Causative organism** | *Streptococcus pneumoniae* (classic) | Various organisms; aspiration, immunocompromised | ### Why This Feature Discriminates **High-Yield:** The **consolidation respecting lobar boundaries** is the single best radiological discriminator. Lobar pneumonia produces a sharply demarcated opacity confined to one lobe; bronchopneumonia produces ill-defined, patchy infiltrates that do not follow anatomical lobar lines. **Clinical Pearl:** Air bronchograms (branching lucencies within consolidation) are present in both but are more conspicuous and uniform in lobar pneumonia. However, they are not discriminatory because they can occur in bronchopneumonia as well. ### Mnemonic **LOBAR:** **L**obe-respecting, **O**rganized consolidation, **B**oundary-defined, **A**ir bronchograms prominent, **R**estrictive anatomy. **BRONCHO:** **B**ronchus-centered, **R**amifying along airways, **O**verlapping lobes, **N**o anatomical respect, **C**hronic/aspiration risk, **H**eterogeneous, **O**ften multifocal. [cite:Robbins 10e Ch 15]
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