Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac size is normal . Cardiomediastinum is shifted toward the left as before . Elevation of the left hemidiaphragm is unchanged . There is no evident pneumothorax . Left lower lobe retrocardiac opacities have markedly improved consistent with improving atelectasis , amount of pleural effusion is likely small . Right lower lobe opacities are likely atelectasis . Contrast is seen in the colon . Left chest wall subcutaneous gas collection has minimally improved
    OUTPUT:
    
Improved aeration in the left lower lobe