Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single frontal image of the chest . Retrocardiac opacity , possibly representing atelectasis but can not exclude pneumonia or aspiration in the right clinical setting . The left costophrenic angle not well visualized , likely representing a small pleural effusion . The lungs are otherwise hyperexpanded but clear . There is no right pleural effusion . There is no pneumothorax . The cardiomediastinal silhouette is unremarkable .
    OUTPUT:
    
Retrocardiac opacity and a probable small left pleural effusion . Findings could represent atelectasis , but can not exclude pneumonia or aspiration in the right clinical setting .