History: 27 yo male with abominal pain
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It can be tough on just two images, but the history was meant to help. Notice the severe wall thickening and hyperenhancement of the terminal ileum entering to colon.
Good didactic info: http://www.learningradiology.com/notes/ginotes/crohnsdiseasepage.htm
Nice review article: http://pubs.rsna.org/doi/pdf/10.1148/rg.243035120