I was 18 when I was diagnosed. They tried the top down approach on me as well. My GI was in way over his head and they did mild medications with me for over a year while the Crohn's marched through my system. I suffered dearly until I was a 18 year old 6'1 male and was 93 pounds.
That's great they are going to take a look with the extended endoscopy. Biologics seem really scary and the side effects are scary. If I could do it over again I would have gone with aggressive medications sooner. I'm 31 now. I lost most of my 20's being sick, taking endless medications. The GI was just too afraid to put a "Kid" on some of those harder drugs. And the Crohns got way too strong and I had to do surgeries. I'm not saying that's going to happen to you just sharing my story.
I found a biologic that worked for me. Stelera. That combined with a hydration regimen and proper diet and some supplements I take and now I'm flying.
So don't get too discouraged. They took my entire large intestine and my intestines I have left have major scarring. But I live a normal life now.
Stick up for yourself in those appoints. Ask questions.
Sending well wishes