Achalasia

     1) Esophageal dilation is best appreciated on lateral chest x-ray , fluid - filled  dilated esophagus is seen to displace the trachea and carina forward
    -When esophagus is dilated , it displaces the displaces the lung behind the right half of trachea (forming posterior tracheal stripe), so the posterior tracheal stripe appears thickened on lateral chest radiograph

    * if thickened post.tracheal stripe is seen in association with anterior bowing of trachea and anterior displacement of carina (esophageal dilation can be confidentally diagnosed )

    2) Frontal radiograph - absence of air in in the expected location of stomach    bubble
      -Air-fluid level within the dilated esophagus is noted