Hi there, Dr. E from the ER here...
Your MRI shows that your L5 vertebrae is pushed slightly forward on S1 vertebrae, but with no obvious nerve findings.
As for ankylosing spondylitis, the finding of edema in the ilia does suggest ankylosing spondylitis - in fact it is diagnostic of it! If the radiologist is diagnosing edema within the joint between the sacrum and ilia, then that is called synovitis and it is not necessarily diagnostic. But i'm 90% sure that this report is diagnostic for AS.
By the way, not too many things cause ulcers in the terminal ileum other than Crohn's, and Crohn's and AS are intertwined with each other!
I hope t his helped,