Find the consolidation and name its lobe by the borders it silhouettes, then look for what changes management — effusion or empyema, cavitation, and an underlying obstructing lesion.
Orient first
- Pneumonia is a clinical diagnosis supported by a new opacity; imaging localises it, finds complications and looks for a mimic or a cause.
- Lobar consolidation is localised by the silhouette sign: loss of a heart border places it in the middle lobe or lingula, loss of a hemidiaphragm places it in a lower lobe.
- Radiological resolution lags clinical recovery by weeks; a follow-up study is for persistence or an underlying lesion, not for day-3 improvement.
Acquire the study
- PA erect radiograph at full inspiration; lateral when a lobe is uncertain; supine AP only when the patient cannot stand.
The manoeuvre
- Find the opacity and its air bronchograms; decide lobar, segmental, patchy (bronchopneumonia) or interstitial.
- Silhouette sign: right heart border (middle lobe), left heart border (lingula), hemidiaphragm (lower lobes), aortic knuckle (apicoposterior left upper lobe).
- Costophrenic angles and a lateral radiograph for effusion; a meniscus larger than blunting suggests a significant effusion.
- Cavitation: an air-fluid level inside the consolidation (Staphylococcus, Klebsiella, tuberculosis, anaerobes).
- Hilum and the airway: a hilar mass or collapse behind the consolidation (post-obstructive pneumonia in an adult smoker).
What confirms it
- A new consolidation in the clinical setting of infection, localised to a lobe or segment.
What licenses you to exclude it
- A clear radiograph argues against lobar pneumonia but does not exclude early or atypical infection — say so in a septic patient.
The classic misread
- Calling crowded vessels on a supine or poor-inspiration radiograph a lower-lobe pneumonia.