Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral radiographs of the chest demonstrate stable heart size , cardiac and mediastinal contours . Opacity at the left lung base has improved compared to the prior study . There may be trace bilateral effusions . No pneumothorax is seen . No displaced rib fracture identified .
    OUTPUT:
    
Improvement in left lower lobe opacity with no definite new opacities .