Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The main pulmonary artery contour is prominent . Streaky opacities at the left lung base suggest atelectasis with increased volume loss since the prior study although similar findings were already present but with better aeration . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Increased opacity at the left lung base , probably consistent with increased volume loss superimposed on chronic scarring and atelectasis , although an infectious process is not excluded .