Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A PICC line has been removed . The patient is status post sternotomy . Dense mitral annular calcifications are again present . The heart is moderately enlarged . There is similar relative elevation of the right hemidiaphragm . Lung volumes are low . On the right , blunting of the right costophrenic sulcus is again noted making it difficult to exclude a small pleural effusion . Confluent opacification is noted in the left retrocardiac region with obscuration of the left hemidiaphragm . Accordingly , parenchymal opacification is suspected and a pleural effusion is difficult to exclude . Pneumonia or atelectasis could explain the findings . Persistent apical pleural thickening on the left may reflect slight scarring , which appears unchanged .
    OUTPUT:
    
Persistent left retrocardiac opacity . Differential considerations include extensive atelectasis or pneumonia ; also a pleural effusion can not be excluded in the area .