This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Surgery
[{'content': 'Amyl nitrate inhalation test is used to detect \nSelect and explain. \nA. Carcinoma esophagus, B. Achalasia cardia, C. Oesophageal diveiculum, D. Transeoesophageal fistula', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Amyl nitrate inhalation (useful adjunct to the radiographic examination)seems to distinguish patients with pseudoachalasia from those with idiopathic achalasia. *In pseudoachalasia patients with tumour infiltration of the distal oesophagus, the narrow lower oesophagal sphincter segment was unaffected by the smooth-muscle relaxant effect of amyl nitrite. *amyl nitrate caused a measurable increase of 2 mm or more in sphincter diameter in patients with idiopathic achalasia ( smooth-muscle relaxant effect of amyl nitrite).', 'role': 'assistant'}]