Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable view of the chest and upper abdomen . This exam is limited due to positioning of the patient . Low lung volumes . A new retrocardiac opacity may represent atelectasis or pneumonia . The cardiomediastinal and hilar contours are grossly stable . No large pleural effusion . No pneumothorax .
    OUTPUT:
    
Limited study , however a new retrocardiac opacity may represent atelectasis or pneumonia .