This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': "A patient with intestinal malabsorption is found to markedly improve when flour products (bread, noodles, etc.) are removed from his diet. At the height of the patient's disease, marked histologic changes would be seen at which of the following sites? \nSelect and explain. \nA. Distal large bowel, B. Distal small bowel, C. Entire large bowel, D. Proximal small bowel", 'role': 'user'}, {'content': 'Answer: D \nExplanation: The patient has celiac disease, which is apparently an acquired hypersensitivity to the gluten (such as gliadin) in wheat. Unlike tropical sprue (which may be related to enterotoxigenic E. coli infection), which involves the entire small bowel, celiac sprue is usually limited to the proximal small bowel. This may occur because the gluten antigens have not yet been digested at this point in their journey through the bowel. A gluten-free diet usually restores the small bowel mucosa.', 'role': 'assistant'}]