This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: GIT and hepatobiliary system, Subject name: Radiology
[{'content': 'Investigation of choice in diffuse esophageal spasm is - \nSelect and explain. \nA. Manometry, B. Esophagoscopy, C. Barium examination showing teiary contractions, D. CT thorax', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Diffuse esophageal spasm (DES) Motility disorder of the esophagus Representing uncoordinated teiary contractions of the esophagus, Corkscrew esophagus is associated with diffuse esophageal spasm On barium swallow, DES may appear as a corkscrew or rosary bead esophagus, but this is uncommon. Manometry is the gold-standard diagnostic test / investigation of choice. Differential Diagnosis * Hypercontracting esophagus (nutcracker esophagus) has normal peristalsis but high manometric intra-esophageal pressures o Barium swallow will be normal or show dysmotility', 'role': 'assistant'}]