A 28-year-old male presents with acute onset dyspnea and pleuritic chest pain. Chest X-ray shows a pneumothorax. Which of the following radiological signs is NOT characteristic of pneumothorax on plain radiography?

## Radiological Signs of Pneumothorax **Key Point:** Pneumothorax is characterized by air in the pleural space, which produces specific and recognizable radiological signs on chest X-ray. The hallmark finding is the **visceral pleural line** — a thin, sharp, radiolucent line that represents the edge of the collapsed lung. ### Classic CXR Findings in Pneumothorax | Finding | Description | Significance | |---------|-------------|---------------| | **Visceral pleural line** | Thin radiolucent line parallel to chest wall | Pathognomonic; marks the lung edge | | **Absence of lung markings** | No vascular/bronchial markings beyond pleural line | Confirms air-filled pleural space | | **Mediastinal shift** | Shift toward collapsed lung (tension PTX) or away (simple PTX) | Indicates pressure effects; tension PTX is surgical emergency | | **Increased lucency** | Hemithorax appears darker/more radiolucent | Due to air replacing lung tissue | | **Consolidation pattern** | Increased opacity with alveolar filling | **NOT seen in uncomplicated pneumothorax** | **High-Yield:** Consolidation (increased opacity with alveolar pattern) is the OPPOSITE of what you see in pneumothorax. Consolidation indicates fluid or cellular infiltrate filling alveoli — the antithesis of air-filled pleural space. This is a classic distractor in pneumothorax questions. ### Why Each Sign Appears 1. **Visceral pleural line** — Direct visualization of the lung edge as it collapses away from the chest wall 2. **Absent lung markings** — The pleural space is filled with air, not lung tissue with vasculature 3. **Mediastinal shift** — In tension pneumothorax, positive pressure pushes mediastinum toward opposite side; in simple PTX, may shift toward collapsed lung due to atelectasis 4. **Consolidation** — Would indicate pneumonia, aspiration, or pulmonary edema — NOT pneumothorax **Clinical Pearl:** If you see consolidation on a CXR in a patient with suspected pneumothorax, think of **secondary pneumothorax** (e.g., from ruptured bulla in COPD with concurrent infection) or **misdiagnosis** — the consolidation is the primary pathology, not the pneumothorax. **Tip:** On exam, when asked "which is NOT a sign of pneumothorax," look for findings that represent lung FILLING (consolidation, opacification) rather than lung COLLAPSE (lucency, absent markings).