Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest were obtained . Poorly defined left retrocardiac opacity is somewhat less conspicuous compared with the prior exam . Findings could reflect atelectasis or chronic aspiration . There is no large pleural effusion or pneumothorax . Cardiomediastinal silhouette appears unchanged . Bony structures are intact .
    OUTPUT:
    
Decreased conspicuity of left lower lobe opacity which could reflect chronic aspiration / atelectasis .