Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable view of the chest . Retrocardiac opacity may indicate infection or atelectasis . There is atelectasis at the left lung base . No focal consolidation to suggest pneumonia . No pleural effusion or pneumothorax . The cardiomediastinal and hilar contours are normal .
    OUTPUT:
    
Left basilar atelectasis . Retrocardiac opacity may indicate infection or atelectasis .