Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a retrocardiac lucency with a thick wall . Question if this is related to a hiatal hernia , but none seen on prior barium swallow study . Does not appear to correspond to known epiphrenic diverticula . Can not exclude a pulmonary process . Linear atelectasis is seen in the left mid lung . There is no effusion or pneumothorax . The there is mild cardiomegaly . There are old right sided rib deformites .
    OUTPUT:
    
Retrocardiac lucency with a thick wall . Question whether this is related to a hiatal hernia , but given that none was seen on the prior barium swallow , pulmonary process not excluded . PA and lateral views or CT scan of the chest may be helpful to further evaluate .