Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable frontal chest radiograph demonstrates hypoinflated lungs with crowding of vasculature and bilateral lower lobe atelectasis . Retrocardiac opacity with trace pleural effusion . Persistent elevation of left hemidiaphragm . Heart size , mediastinal contour , and hila are otherwise unremarkable . Limited assessment of the upper abdomen is within normal limits .
    OUTPUT:
    
Retrocardiac opacity with trace left pleural effusion is worrisome for pneumonia .