Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest provided . There is improved aeration at the right lung base as compared with the prior study . Evaluation is somewhat limited due to patient 's rotation to her left on the frontal radiograph . There is a left pleural effusion which is moderate in size and appears stable to slightly increased from prior exam . There is probable compressive left lower lobe atelectasis . Difficult to exclude an underlying pneumonia . No pneumothorax . Heart size can not be assessed . The mediastinal contour appears grossly stable . No acute bony abnormalities are detected .
    OUTPUT:
    
Moderate left pleural effusion with left basal atelectasis , can not exclude pneumonia . Improved aeration at the right lung base .