Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Retrocardiac opacification could be due to atelectasis , although an infectious process can not be excluded . There is minimal right basilar atelectasis . Pulmonary vascular congestion is seen without evidence of interstitial pulmonary edema . A small left pleural effusion is possible . There is no right pleural effusion . No pneumothorax is seen . The heart size is normal . The mediastinal contours are normal .
    OUTPUT:
    
1 . Left retrocardiac opacification could be atelectasis or infection . 2 . Pulmonary vascular congestion without evidence of interstitial edema . 3 . Possible small left pleural effusion .