Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Semi-upright portable chest radiograph is obtained . There is a large left pleural effusion with associated compressive atelectasis in the left mid and lower lung . There is aeration in the left upper lobe . The right lung is clear . Heart size can not be assessed . Mediastinal contour is notable for a densely calcified aortic knob . Bony structures are intact .
    OUTPUT:
    
Large left pleural effusion with associated lower lung atelectasis . Please note underlying pneumonia can not be excluded . Recommend followup to resolution .