A 72-year-old woman with advanced lung cancer is admitted with acute dyspnea and hemoptysis. Chest X-ray shows a sharply demarcated opacity in the left upper lobe with a straight medial border. The left hilum is elevated, and the trachea is deviated toward the left. The left hemithorax appears smaller than the right. What is the primary radiological diagnosis?

Explanation

## Collapse: Radiological Signs and Clinical Context **Key Point:** Collapse (atelectasis) is characterized by volume loss, mediastinal shift toward the affected lobe, elevated hilum, and tracheal deviation. Air bronchograms are **absent** because the airways are obstructed. ### Radiological Features of Collapse (Atelectasis) | Sign | Significance | |------|---------------| | **Straight medial border** | Indicates volume loss and lobe retraction | | **Elevated hilum** | Pulled upward by collapsed lobe | | **Tracheal deviation** | Toward the collapsed side (mediastinal shift) | | **Reduced hemithorax size** | Volume loss is the hallmark | | **Absent air bronchograms** | Airways are obstructed, not patent | | **Sharp, linear borders** | Characteristic of atelectasis | **High-Yield:** The **combination of mediastinal shift + elevated hilum + tracheal deviation + volume loss** = collapse, not consolidation. ### Why This Is Collapse, Not Consolidation 1. **Straight medial border** — indicates retraction and volume loss (consolidation has ill-defined or convex borders) 2. **Elevated hilum** — pulled upward by the collapsed lobe 3. **Tracheal deviation toward the left** — mediastinal shift toward the atelectatic lobe 4. **Smaller left hemithorax** — volume loss is pathognomonic for collapse 5. **Clinical context** — central lung cancer causing airway obstruction is a classic cause of collapse 6. **No mention of air bronchograms** — airways are obstructed, not patent **Clinical Pearl:** Post-obstructive pneumonia can occur *distal* to a collapsed lobe, but the primary finding here is collapse itself. The hemoptysis and dyspnea reflect the obstructing tumor. **Mnemonic:** **SHIFT** = Straight borders, Hilum elevated, Increased density, Flat/reduced volume, Trachea deviated ```mermaid flowchart TD A[Acute dyspnea + hemoptysis in lung cancer]:::outcome --> B{Hilum elevated + tracheal deviation?}:::decision B -->|Yes| C[Mediastinal shift present]:::action C --> D{Volume loss?}:::decision D -->|Yes| E[Collapse/Atelectasis]:::outcome D -->|No| F[Consolidation or effusion]:::outcome B -->|No| G[Rule out collapse]:::action G --> H{Air bronchograms visible?}:::decision H -->|Yes| I[Consolidation]:::outcome H -->|No| J[Effusion or mass]:::outcome ```