Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes remain low . Small the moderate bilateral effusions , larger on the right are again noted . There is more dense opacity in the retrocardiac region . Mild pulmonary edema may be slightly worse compared to prior . Median sternotomy wires and cardiomegaly are unchanged . No acute osseous abnormalities .
    OUTPUT:
    
Persistent small to moderate bilateral pleural effusions , larger on the right . Superimposed retrocardiac opacity is noted , potentially in part due to atelectasis although infection at either base would be difficult to exclude . Mild pulmonary edema .