Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared with the prior radiograph , lung volumes are significantly lower with evidence of increased pulmonary vascular congestion . A left retrocardiac opacity may be due to atelectasis , but pneumonia can not be excluded in this clinical setting . Mild cardiomegaly is unchanged . Intact median sternotomy wires and mediastinal clips are unchanged .
    OUTPUT:
    
1 . Left retrocardiac opacity may be due to atelectasis , but pneumonia can not be excluded , given this clinical setting . 2 . Notably lower lung volumes with increased pulmonary vascular congestion .