Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are low , resulting bronchovascular crowding . Retrocardiac opacification likely represents a combination of collapse and pleural effusion . The heart remains enlarged . The patient is status post median sternotomy , with intact wires . No pneumothorax . .
    OUTPUT:
    
Retrocardiac opacity likely represents a combination of collapse and pleural effusion , however pneumonia could also be considered in the appropriate clinical setting .