Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is again moderate to severely enlarged . Opacification in the retrocardiac area of the left lower lobe persists . Although it is nonspecific as to etiology , it could probably be explained by atelectasis associated with marked cardiomegaly . There is mild upper zone re-distribution of pulmonary vascularity but findings suggesting pulmonary congestion are not as striking as on the prior examination . There is no pleural effusion or pneumothorax . Mild degenerative changes are present along the thoracic spine .
    OUTPUT:
    
Marked cardiomegaly . Opacity in the left lower lobe , which is nonspecific . Although pneumonia could be considered , there has been fairly little if any change and such an opacity could also be seen with atelectasis associated with marked cardiomegaly .