Retrocardiac lucency with air fluid level is seen in
Paraoesophageal hiatus hernia('Rolling hernia')may be visible on a plain radiograph of the chest as a gas bubble,often with a fluid level behind the hea.It is herniation of stomach fundus or rarely other abdominal contents through a hiatus,usually towards left side. Reference:Bailey & Love's sho practise of surgery,25 th edition,page no:1024;SRB's manual of surgery,5th edition,page no:795.
Hiatus hernia
Distal end esophageal obstruction
Eventration of diaphragm
None
Cardio thoracic surgery  