These lung ultrasound images demonstrate a rare and fascinating finding in a patient with bullous emphysema. The patient initially presented with septic shock due to pneumonia and showed clinical improvement with antibiotic therapy, though they continued to require supplemental oxygen when this study was performed.

The POCUS images are from the right lower lung zone. At first glance, the findings might resemble a complex pleural effusion that we discussed before. However, on closer inspection, the pleural fluid surrounding these appears anechoic, and the cyst-like structures are clearly in continuity with the lung parenchyma, a connection that’s even more evident in Figure 2.

Reviewing the patient’s CT scan from a week earlier revealed extensive bullous disease predominantly involving the lung bases, in addition to pneumonia. Given these findings, the most likely explanation for the POCUS images is fluid-filled bullae. Normally, air-filled bullae would not appear anechoic on ultrasound. It’s hypothesized that inflammation in the surrounding lung may cause fluid to accumulate within the bullae. Whether this fluid is sterile or infected is uncertain without direct sampling (rarely performed).

In our case, thoracentesis was performed, and the pleural fluid analysis revealed a transudative profile with a pH of 7.5, supporting the idea that the process was mostly reactionary given the patient’s clinical improvement.

The main differential diagnosis for similar POCUS findings includes pre-existing cystic lung disease, but this was unlikely here since no cysts were seen on the prior CT imaging. Special thanks to Dr. Miller for suggesting the accurate diagnosis. As rare as this phenomenon is, even many POCUS experts have never encountered it. Below are two additional images.