I don't know if this helps, or is even pertinent... for those who want to see actual scar tissue, I posted some pics on here (someplace) of mine. My disease has only "officially" involved my colon (the laproscopic surgery was never biopsied, so 'disease' in the upper tract has never been confirmed).. but in the colon I have had both Crohns N Ulcerative colitis.. and you can see in the scar tissue formations what can typically happen. There are stalagmites/stalagtites of tissue.. some joined, even forming like a peace symbol. These appear to be internal fistulas... spanning the much larger diameter of the large colon.. There is also a lump of scar tissue... you can see how it changes the shape of the colon from a circle, to a crescent moon... just accumulated on one side, narrowing down the passage.. a stricture. Picture these formations in the much smaller upper GI tract.. and it helps formulate an idea of how bad it can be..and how scar tissue doesn't follow 2 dimensional thinking. I 'used' to assume scarring inside me would be like, say a sunburn on my arm.. only inverted. My 'imagination' didn't do the actual disease justice.
Like, those photos aren't for the squemish, and there is a definite distinction between the lower & upper tracts.. but if one wants a close visual approximation, feel free to look