The appearances of achalasia are almost pathognomonic on barium swallow. These include:
- a gas-filled dilated esophagus on control film
- a distended esophagus with an air-fluid level
- an adynamic esophagus
- a distal acute taper of the esophagus with a bird-beak appearance.
The bird-beak sign is used to refer to the tapering of the inferior esophagus in achalasia. This has a smooth outline implying a non-malignant cause. A rat's tail appearance is used interchangeably.