A barium swallow is able to confirm that:

• bird beak sign
• esophageal dilatation
• pooling or stasis of barium in the esophagus when the esophagus has become atonic or non-contractile (a late feature in the disease)
• incomplete lower esophageal sphincter relaxation that is not coordinated with esophageal contraction
• failure of normal peristalsis to clear the esophagus of barium when the patient is in the recumbent position, with no primary waves identified
• uncoordinated, non-propulsive, tertiary contractions 
• when barium column is high enough (patient standing) the hydrostatic pressure can overcome the lower esophageal sphincter pressure allowing passage of esophageal content