Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is mild patchy retrocardiac opacification , which may represent atelectasis . No additional focal consolidations . No pulmonary edema . Normal cardiomediastinal silhouette . No pleural effusion . No pneumothorax .
    OUTPUT:
    
Patchy retrocardiac opacification , which may represent atelectasis , however a pneumonia can not be entirely excluded .