My doc explained and I am of the belief that there are different "causes" of "pouchitis" or inflammation of the pouch, and there are no easy diagnostic test to determine what the "cause" is. This is why docs will often cycle through the treatments in the pouchitis article I posted earlier in this thread first (and then biologics, which came along after the article was written), to see if you can get a good response. If chronic rotating antibiotics stop symptoms and clear up inflammation on scope, great-and probably not "IBD of the pouch or Crohns of the pouch" If it takes immuran and/or biologics to successfully treat, it is probably some ityoe of IBD-related root cause.
I was adamant when I started hearing "it may be crohns" because I was mainly worried that it might mean I was now susaceptibke to disease throughout my digestive system, and in 30 years there had never been signs of that. Any inflamation i have now is restricted to the pouch.i like to think of it as "IBD of the pouch". If someone asks, I say I have an inflammatory bowel disease. I don't say UC, and I don't say Crohns, and frankly, if you don't have a pouch "pouchitis" just prompts more questions. But ultimately what I call it doesn't matter because I have found a treatment that works (immuran plus rotating antibiotics) and if/when that stops working, I will start on one of the biologics.
If it is not clear cut crohns diagnosis, I see no reason why you couldn't start with rotating antibiotic treatment (maybe with budesonide-a designer, non-systemic steroid to jump start healing of inflammation), then if it doesn't work try something else or or if you start to feel uncomfortable with long term antibiotics and more comfortable with another treatment, go that route. BIOLOGICS as a first line treatment is not an unreasonable choice if it is what YOU want, but if you'd rather wait on that treatment and try other things first, there is no reason not to.