Forty-three patients in whom standard radiographic projections of the chest suggested effusion in the dorsal costophrenic sinus were also examined in sitting, forward-leaning position. Following this change of posture the sinus cleared if the effusion was free. The procedure can therefore be useful in patients in whom there is difficulty in distinguishing between free and encapsulated pleural fluid. In addition, it facilitates assessment of the posterior parts of the lungs and the pleura that otherwise are concealed by free effusion.
