Emergency pleural ultrasound is a highly sensitive and specific imaging diagnostic technique that plays a very important role in the diagnosis and treatment of current pleural diseases.

The diaphragmatic margin sign is a small triangular abnormality that obscures the normal shape of the diaphragm. It is secondary to atelectasis in the upper lobe. It is caused by traction on the pleura or the greater interlobar fissure and the subpleural ligament.