A 30-year-old man was referred to a surgeon because he has been having increasing difficulty swallowing both solids and liquids. Physical examination of the patient is noncontributory. The patient swallows a barium solution, with continuous fluoroscopy (X-ray recording) is shown below. Esophageal manometry shows incomplete relaxation of the lower esophageal sphincter in response to swallowing, high resting lower esophageal pressure, and absent esophageal peristalsis. The manometry and barium swallow studies most strongly suppo which of the following diagnoses?

The most likely diagnosis is achalasia. This condition is a neurogenic esophageal disorder that can occur at any age, but frequently is diagnosed when individuals are between the ages of 20 and 40. Characteristically, the swallowing difficulties involve both solid food and liquids. The manometry findings illustrated are typical; There is acute tapering at the lower esophageal sphincter and narrowing at the gastroesophageal junction, producing a "bird's beak" or "rat's tail" appearance. Larger cancers of the esophagus would be more likely to cause either a mass or an ulceration, which would be visible on barium swallow. Very small cancers and Barrett's esophagus would require esophagogastroduodenoscopy with biopsy for diagnosis, and would be unlikely to cause dysphagia.