Pleural effusion. Longitudinal scan at the PLAPS point. The pleural effusion is defined not because of (as shown here) a hypoechoic tone but by the appearance of the lung line (lower white arrows), which indicates the visceral pleura. The pleural line, which is clearly visible (upper white arrows) indicates here only the parietal pleura. All effusions, anechoic or echoic, can be diagnosed using the lung line. The volume of this effusion can be measured using a simple index. Note the underlying nontranslobar lung consolidation (subpleural, of course) with the shred sign (black arrows). The quad sign just describes the rough trapezium defined by the pleural line, the shadow of the ribs and the lung line. This is a typical example of (mixed) PLAPS.