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
Barrets esophagus involves most commonly which pa of esophagus 
Select and explain. 
A. Upper 1\/3rd, B. lower 1\/3rd, C. Middle 1\/3rd, D. Diffuse
B: lower 1\/3rd
Answer: B: lower 1\/3rd 
Explanation: BARRETT'S OESOPHAGUS * It is the metaplastic changes in the mucosa of the oesophagus as the result of GERD. * Squamous epithelium of lower end of the oesophagus is replaced by diseased columnar epithelium (columnar metaplasia). * There is a macroscopically visible length of columnar mucosa with microscopic features of intestinal metaplasia. * It affects lower oesophagus commonly often middle oesophagus also. Ref: SRB&;s manual of surgery,3 rd ed , pg no 728