Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable view of the chest demonstrates low lung volumes , which accentuate bronchovascular markings . Subtle retrocardiac opcity may be due to atelectasis . No large pleural effusion , or pneumothorax . Hilar and mediastinal silhouettes are unchanged . Heart is mildly enlarged . Minimal perihilar vascular congestion is noted .
    OUTPUT:
    
1 . Subtle retrocardiac opacity , may represent atelectasis , aspiration or infection in the appropriate clinical setting .