Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal and hilar contours are normal . Subtle linear horizontally oriented opacities in the left costophrenic angle appear improved compared to prior exams and likely reflect the sequelae of resolving atelectasis . There is no pneumothorax . A small left pleural effusion is seen .
    OUTPUT:
    
Small left pleural effusion and improving atelectasis , but no pneumothorax .