Which of the following radiological signs is characteristic of lobar collapse but NOT seen in consolidation?

Explanation

## Distinguishing Collapse from Consolidation **Key Point:** Fissural displacement is the hallmark sign of lobar collapse and is absent in simple consolidation. This occurs because the collapsed lobe shrinks and pulls the pleural fissures inward. ### Radiological Signs Comparison | Feature | Consolidation | Collapse | |---------|---|---| | **Fissural displacement** | Absent | Present (inward shift) | | **Air bronchogram** | Present | Absent or obscured | | **Silhouette sign** | May occur | May occur | | **Volume** | Normal or increased | Decreased | | **Opacity** | Increased | Increased | | **Mediastinal shift** | Absent | Present (toward collapsed side) | **High-Yield:** The **displacement of fissures** is the single most reliable radiological sign to differentiate collapse from consolidation. In collapse, fissures move inward (toward the hilum); in consolidation, they remain in their normal position. **Clinical Pearl:** Air bronchograms are seen in consolidation (air-filled bronchi stand out against opacified lung) but are typically absent in collapse because the bronchi are compressed and may contain fluid or secretions. **Mnemonic - COLLAPSE signs:** **C**ontraction of volume, **O**bliteration of fissures (displacement), **L**oss of air bronchogram, **L**ateral shift of mediastinum, **A**bsence of normal landmarks, **P**leural folds, **S**ilhouette sign (may occur). ### Why Silhouette Sign Occurs in Both The silhouette sign (loss of cardiac or mediastinal border) can occur in both consolidation and collapse when the opacified/collapsed lobe is adjacent to the mediastinum. It is therefore NOT specific to collapse.