Pneumothorax: High-Yield Radiology Essentials
1. Classic Radiographic Signs
- Visceral Pleural Line: A thin, white line representing the edge of the collapsed lung. Lung markings are absent beyond this line (the “peripheral hyperlucency” zone).
- Expiratory Films: Taking an X-ray in expiration may make a small, occult pneumothorax more apparent by decreasing lung volume while the air volume in the pleural space remains constant.
- Deep Sulcus Sign: A sign of pneumothorax on a supine chest X-ray. The costophrenic angle appears abnormally deep, dark, and sharp because the air collects anteriorly and inferiorly.
2. Tension Pneumothorax Features
This is a clinical diagnosis; do not delay treatment for imaging. If seen on film, look for:
- Mediastinal Shift: The trachea and heart are pushed away from the side of the pneumothorax.
- Diaphragmatic Inversion: The hemidiaphragm on the affected side appears flattened or even pushed downwards.
- Widened Intercostal Spaces: Due to increased intrathoracic pressure on the affected side.
3. Examination Pearls
| Imaging Scenario | Radiological Pearl |
|---|---|
| Skin Folds | Can mimic a pleural line. Unlike a true pneumothorax, lung markings are visible beyond the skin fold line. |
| Bullae | Can be confused with pneumothorax. Bullae have very thin walls and are surrounded by lung tissue, not air-filled pleural space. |
| Ultrasound | The “Lung Point” sign is highly specific for pneumothorax; “Lung sliding” (comet-tail artifacts) is absent in pneumothorax. |