Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable upright view of the chest . A left retrocardiac opacity . Remains stable since the ___ CT , reflecting underlying atelectasis . Underlying consolidation can not be excluded . The right lung is clear . There is no pneumothorax or large pleural effusion . A transesophageal catheter extends to at least the level of the stomach , with the tip excluded from this examination .
    OUTPUT:
    
Persistent left retrocardiac opacity , likely reflecting severe atelectasis also seen on the ___ CT . Underlying consolidation can not be excluded . The right lung is clear .