What is typically observed on a barium swallow in a patient with achalasia?

In achalasia, a condition characterized by the failure of the lower esophageal sphincter to relax and impaired peristalsis of the esophagus, the barium swallow reveals a classic "bird's beak appearance." This radiological finding occurs because the esophagus becomes dilated above the level of the lower esophageal sphincter, which is narrowed or obstructed. The "beak" refers to the tapered point at the distal end of the esophagus formed by the failure of the sphincter to open properly during swallowing.

This distinctive appearance is significant in the diagnosis of achalasia and helps to differentiate it from other esophageal conditions. Other options such as strictures, tumors, and diverticula do not produce this characteristic radiological finding. Strictures may appear as narrowing without the characteristic tapering observed in achalasia, while tumors could show irregular masses rather than a consistent narrowing pattern. Diverticula, on the other hand, may present as outpouchings rather than a focal narrowing at the lower esophagus. The "bird's beak" appearance, therefore, specifically signifies the pathophysiological changes associated with achalasia.