Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Small left pleural effusion has decreased when compared to the prior . There is a small amount of residual atelectasis in the left lower lobe . The appearance of the lungs are otherwise unchanged . Mild cardiomegaly with prior median sternotomy mitral valve repair . No pneumothorax .
    OUTPUT:
    
Interval decrease in the left small pleural effusion .