Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Increase in the left retrocardiac density since ___ likely reflects worsening atelectasis and possible small left pleural effusion , however , underlying consolidation can not be excluded . There is no pneumothorax . The right lung appears clear . The heart size is top normal . The hilar and mediastinal contours remain within normal limits .
    OUTPUT:
    
Increased left retrocardiac density likely reflects increased atelectasis , however , consolidation can not be excluded .