Which diagnostic test demonstrates a bird-beak appearance in achalasia?

• A. Barium swallow
• B. Endoscopy
• C. MRI
• D. Ultrasound

Answer: (A)

The main concept here is the radiographic hallmark of achalasia seen on contrast imaging. On a barium swallow, the esophagus becomes dilated from impaired relaxation of the lower esophageal sphincter, and the contrast tapers abruptly at the gastroesophageal junction. This produces a slender, pointed contour that researchers describe as a bird-beak appearance. This sign is best demonstrated by barium swallow because it directly outlines the shape and caliber of the esophagus and LES.

Endoscopy can show a dilated esophagus and help rule out a mechanical obstruction, but it does not reliably reveal the bird-beak taper at the LES. MRI and ultrasound are not standard for diagnosing achalasia and do not typically show the characteristic bird-beak sign. Definite confirmation is usually by esophageal manometry, which measures LES relaxation and esophageal peristalsis, but the question focuses on which test visualizes the bird-beak sign.