Introduction with a case
Lung point: Diagnostic of pneumothorax
Hydro-point: Diagnostic of pleural air-fluid level
Below is a schematic of what is seen on this video. This video is zoomed in more than most, so the entire pleural effusion cannot be seen:
To make a secure diagnosis of hydropneumothorax, the following three components should be seen. These points correspond to the figure:
[C] Inferior to the air-fluid level, the ultrasound should show a pleural effusion.
Differential diagnosis of hydro-point
|Lung abscess creating an air-fluid level (white arrowhead). This may be differentiated from hydro-point because it does not contact the pleura. From Lin 2004|
Obtaining additional information from a thoracic ultrasound containing hydro-point
|Lin 2001 found suspended micro-bubbles in 8/8 cases of pyopneumothorax and no cases of uninfected hydropneumothorax. However, a later study by Chen 2009 found microbubles in only 23% of pyopneumothorax cases. Image from Lin 2001.|
- Hydro-point is the ultrasonographic representation of an air-fluid level in the pleural space. The ultrasound displays rhythmic alternation between showing a pneumothorax and showing a pleural effusion.
- The combination of hydro-point, a pneumothorax anterior to the hydro-point, and a pleural effusion posterior to the hydro-point allows fairly confident diagnosis of an intra-pleural air-fluid interface. This may be caused by hydropneumothorax, hemopneumothorax, or pyopneumothorax.
- Hydro-point should be differentiated from lung point, which reveals alternation between a pneumothorax and normal lung slide and is diagnostic of a pneumothorax.