In patients with achalasia, what is the characteristic feature seen during a barium swallow?

In patients with achalasia, a barium swallow study typically reveals a characteristic "bird beak" appearance at the lower esophagus. This finding occurs due to the failure of the lower esophageal sphincter to relax properly, leading to a tapering of the esophagus at its distal end. As food accumulates in the esophagus due to this obstruction, the proximal part can become significantly dilated, while the narrowed distal segment creates the distinctive beak-like appearance on imaging.

This feature is critical for diagnosing achalasia because it reflects the pathophysiological changes in the esophagus caused by the condition: a combination of increased resting tone of the esophageal sphincter and a lack of coordinated peristalsis in the esophageal body. Recognizing this pattern during a barium swallow can aid clinicians in distinguishing achalasia from other esophageal conditions.