As fluid accumulates in the dependent zones, we normally look for pleural effusion just above the diaphragm aiming the ultrasound beam posteriorly. We have previously talked about the spine sign and jellyfish/whale tail sign encountered in such cases. Here is an interesting case, where we were performing lung ultrasound in a patient with acute kidney injury who was requiring supplemental oxygen. As the transducer is placed in the left upper anterior zone just below the clavicle, we see pleural effusion surrounding atelectatic lung lobes instead of A or B-lines. This indicates that we are looking at a very big effusion. As the fluid is completely black without any echogenicities, it must be either transudate or a fresh hemothorax depending on the context. If you are dealing with a peritoneal dialysis patient, pleuroperitoneal leak is another differential to keep in mind.

Below are more images from various scan points.

As expected, Chest X-ray demonstrated a completely whiteout left lung. Repeat X-ray shows some improvement after draining approximately 1500 mL of pleural fluid.

Follow up ultrasound approximately 12 hours after thoracentesis shows lung re-expansion in the anterior zones (A-lines, one B-line). Lateral zones could not be accessed due to dressings.