Pleural Effusion

Pleural Effusion
Pleural effusion should be evaluated with the ultrasound probe placed as posteriorly as possible in a supine patient to identify fluid layered in the dependent portion of the thorax. Effusion appears as an anechoic (black) area deep to the parietal pleura referred to as the quad sign. The upper boundary of the area is created by the parietal pleura and the lower boundary by the visceral pleura. Movement of the lung toward the pleural line on inspiration creates an alternating pattern on M-mode known as sinusoid sign.