Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . Cardiomegaly is likely mild - to - moderate . There is mild pulmonary edema . There is a small left pleural effusion . More focal opacity in the retrocardiac region may be related to low volumes and atelectasis , however pneumonia can not be excluded .
    OUTPUT:
    
Low lung volumes with suspected superimposed pulmonary edema . More focal opacity in the retrocardiac region may represent a combination of edema and atelectasis , however in the appropriate clinical setting pneumonia can not be excluded .