Fig. 1

a Chest X-ray of the patient with left pleural effusion during the postoperative period of myocardial revascularization. b Patient in the supine position with the head at 30°; ultrasound assessment in the lower thorax on the posterior axillary line. c Quantification of the pleural effusion with a 5-MHz convex transducer; measurement of the distance between the visceral pleura and the posterior wall of the thorax in the transverse axis. In this case, the distance is 26 mm, with an approximate calculated volume of 520 ml by the Balik method. d Thoracentesis kit