This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
Bird beak appearance of esophagus: 
Select and explain. 
A. Achalasia cardia, B. Cancer esophagus, C. Schatzki ring, D. DES
A: Achalasia cardia
Answer: A: Achalasia cardia 
Explanation: Ans. (a) Achalasia cardiaRef: Bailey and Love 26th edition, Page 1014Interesting Barium swallow findings in esophagus:* Bird beak appearance: Achalasia* Rat tail appearance: Cancer esophagus more commonly* Hurst phenomenon: Achalasia* Cork screw appearance: DES* Postcricoid web: Plummer Winson syndrome* Naclerio V sign (Pneumo mediastinum in Xray) - Esophageal Perforation