The most likely diagnosis is achalasia. This patient has dysphagia to both solids and liquids, suggesting a motility disorder. This patient's diagnostic evaluation and associated findings represent the classic presentation of achalasia, which is characterized by dysphagia to solids and liquids, regurgitation, and possibly weight loss, chest pain, and heartburn. Barium radiography shows a dilated esophagus with narrowing at the lower esophageal sphincter, described as a “bird's beak.” Upper endoscopy was performed to rule out mechanical obstruction in the region of the lower esophageal sphincter as a cause of dysphagia. If obstruction is caused by a malignant lesion, the disorder is designated “pseudoachalasia.” Manometry is required to confirm the diagnosis of achalasia.

Diffuse esophageal spasm is a rare hypertonic motility disorder that presents with chest pain or dysphagia. Clinical manifestations are similar to those of angina pectoris. On esophageal manometry, simultaneous high-amplitude (>30 mm Hg) esophageal contractions are seen with intermittent aperistaltic contractions. The barium esophagogram finding of a “corkscrew” esophagus is typical of diffuse esophageal spasm. This patient's manometric and barium radiography findings are not consistent with diffuse esophageal spasm.

Esophageal hypomotility disorders can involve a hypotense lower esophageal sphincter, aperistaltic contractions, or both. In most patients, the cause of the hypotensive esophageal disorder is unknown. However, secondary causes include smooth-muscle relaxants, anticholinergic agents, estrogen, progesterone, connective tissue disorders (such as systemic sclerosis), and pregnancy. Esophageal hypomotility disorders are characterized by low-amplitude contractions on manometry with a hypotensive lower esophageal sphincter; this differs from achalasia, which is characterized by incomplete relaxation of the lower esophageal sphincter. These manometric findings are the opposite of what was found on this patient's manometry, which was consistent with achalasia.

Nutcracker esophagus is a hypertonic motility disorder that is characterized by high-amplitude peristaltic contractions of greater than 220 mm Hg. This patient does not have these manometric findings.