Bird beak sign (esophagus)
The bird's beak sign of the esophagus is used to refer to the tapering of the inferior esophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the rat-tail sign.
The appearance, although classically occurring in primary achalasia, can also occur in pseudoachalasia due to a gastric tumor involving the gastro-esophageal junction.
The term bird's beak sign is used in a number of other contexts: see bird beak sign (disambiguation).