The Spondylitis Association of America has very good information about
all aspects of spondyloarthropathy. It is a great place to start learning about
the family of spondylitis diseases.
http://www.spondylitis.org/main.aspx
In regards to his anemia and weight loss - sounds to me those two problems are good reasons that he had the scopes. Many people with one of the inflammatory bowel diseases [Crohn's or ulcerative colitis] develop spondyloarthropathy. Until he gets the results of his scopes, it is premature to discuss the future in terms of pain, etc. because of the intertwining of the two diseases. If he has no bowel disease, then treatment will probably start differently than if he has both. Also, treatment regimes vary among doctors. Some rheumatologists are much more aggressive than others in what they prescribe.
I have both diseases and I am doing very well for the most part. I do have some pain but then again I am more than twice the age of your SIL and likely have a lot of "wear and tear" issues.