Elevation of the right lung base on the PA view, with a corresponding semicircular contour of the lung base and adjacent linear opacities in the lung parenchyma on the lateral view, suggestive of a loculated pleural effusion. A less likely differential is elevation of the right hemidiaphragm. Further evaluation with pleural ultrasound or CT scan is recommended if clinically indicated.
Loculated pleural effusion (Uncertain)