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
Amyl nitrate inhalation test is used to detect 
Select and explain. 
A. Carcinoma esophagus, B. Achalasia cardia, C. Oesophageal diveiculum, D. Transeoesophageal fistula
B: Achalasia cardia
Answer: B: Achalasia cardia 
Explanation: 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).