Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Moderate left pleural effusion appears marginally smaller when compared to prior . Prior left base pigtail catheter is no longer visualized . The lungs are otherwise clear . There is no pneumothorax . The cardiomediastinal silhouette is within normal limits atherosclerotic calcifications are noted at the aortic arch .
    OUTPUT:
    
Persistent moderate left pleural effusion . No superimposed acute process .