Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs demonstrate unremarkable cardiomediastinal and hilar contours . Minimally increased opacification is noted within the retrocardiac space , particularly evident on the lateral view . Finding may be related to atelectasis exaggerated by slightly low lung volumes , though can not exclude developing infectious process . No pleural effusion or pneumothorax is evident .
    OUTPUT:
    
Minimally increased opacification of retrocardiac space may represent atelectasis , but can not exclude developing pneumonia in the appropriate clinical setting . No overt pulmonary edema .