Pneumothorax
The ultrasound appearance of pneumothorax is discussed here.
Loss of lung sliding and the movement artefact deep to the pleural line
- A pneumothorax lies deep to the smooth parietal pleural surface.
- The gas interface creates a highly reflective surface reflecting all ultrasound energy.
- This prevents imaging of structures lying below the pneumothorax. The movement of the lung, deep to the pneumothorax is completely hidden – lung sliding is lost.
Loss of characteristic B-lines
- B-lines (vertical short path reverberation artefacts) are created by alveolar and interstitial fluid or fibrosis at the lung surface.
- In the same way that pneumothorax hides lung sliding it also hides any B-lines lying below.
Increased clarity of A-lines
- A-lines (horizontal long path reverberation artefacts) are echogenic horizontal artifactual lines deep to the pleural surface that are characteristic of pneumothorax.
- The mirror like, flat parietal pleura overlying the pneumothorax reflects the ultrasound which often then reverberates between the pleural surface and other horizontal reflecting surfaces above. These include fascial planes and the transducer surface itself.
- Multiple reflections cause horizontal linear artefacts mirroring the flat surfaces above the pleural surface, deep to the pleural surface.
Lung Point
- Pneumothorax separates the visceral and parietal pleural surfaces.
- The point at which these surfaces meet is known as the lung point
