Bedside thoracic US found a large heterogeneous left pleural effusion with compressive atelectasis of the ipsilateral lung (Video 1). Furthermore, a hypoechogenic collection was located outside the rib cage at the fifth to sixth intercostal spaces in the anterior axillary line, 5 cm from the surgical scar. Between the extrapleural collection and the pleural space, a to and fro motion in synchrony with respiration was observed on color flow examination and a valve mechanism was detected (Videos 2 and 3). On inspiration, fluid entered the pleural space; on expiration, it left it. To clarify these findings, a thoracic CT scan was performed, which showed the collection outside the rib cage and the connection between it and the pleural space (Fig 2). A left chest tube for drainage was placed and 1,500 mL of serohematic fluid was obtained, with improvement in the patient’s condition. A new thoracic US was performed with only a minimal pleural effusion that remained. A pleural line image appeared in the area where the orifice was previously detected and the to and fro Doppler signal disappeared in the color Doppler study.