It sounds like your IBD serology came back as indeterminate. This is not particularly uncommon. It just means that your antibody results have characteristics of both Crohn’s and UC. It would appear that the more they study IBD, they discover that there is so much more to learn.
The perianal abscesses would likely be from IBD activity, not drug complications. They are more associated with Crohn’s than UC, but are seen in both. In a practical sense, it does not matter unless you are overly concerned about your definitive diagnosis. The main take away is that staying on Entivio is appropriate UNLESS it is time to move to a different biologic because you are not getting enough from the Entivio. It might be worth exploring with your doctor if there is a better choice that is known for better controlling perianal disease. Combination therapy may also be in order. Five years is a long time to be putting up with this!
In regard to diet, the only thing I have heard of that helps some people with gut inflammation is avoiding most processed carbs and sugars.
Jan 