Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single upright AP image of the chest . The lungs are well expanded . There is opacity in the right lung base which could represent patchy atelectasis , early pneumonia or aspiration . Clinical correlation is advised . There is no pleural effusion or pneumothorax . The cardiomediastinal silhouette is mildly enlarged , similar prior exams . Status post median sternotomy .
    OUTPUT:
    
Opacity at right lung base which could represent patchy atelectasis , pneumonia or aspiration . Clinical correlation is advised .