Final answer:
The condition with dysphagia and a 'bird's beak' sign in barium swallow is achalasia, which impairs the movement of food toward the stomach due to lower esophageal sphincter dysfunction.
Step-by-step explanation:
The condition characterized by dysphagia to solids and liquids, where a barium swallow reveals a 'bird's beak' sign, is known as achalasia. Achalasia is a rare disorder of the esophagus which affects its ability to move food toward the stomach. Achalasia is a disorder of the esophagus where the lower esophageal sphincter (LES) fails to relax properly, leading to difficulty in swallowing and the bird's beak appearance on barium swallow studies. During the esophageal phase of deglutition, normally, the lower esophageal sphincter relaxes to allow food to pass into the stomach; however, in achalasia, this sphincter fails to relax properly, leading to difficulty swallowing and the classic bird's beak appearance on imaging.