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: Radiology
Cobble stoning of intestine with string sign of kantor is seen in: 
Select and explain. 
A. Crohn's disease, B. Ulcerative coitis, C. Ishemic colitis, D. Amoebic colitic
A: Crohn's disease
Answer: A: Crohn's disease 
Explanation: Ans. A. Crohn's disease* Cobble stone mucosa is appearance of the intestinal mucosa in Crohn's disease to the endoscopist, Cobblestoning refers to the uniform nodules-due to the sub-mucosal fibrosis.* String sign of Kantor is due to involvement of the terminal ileum in Crohn's disease.* It is caused by severe spasm due to irritability of the loop producing the appearance of a frayed cotton string.* Subsequently the wall of the ileum may become fibrotic and the lumen fixed in diameter.