I wouldn't tell you to do or not do that because if something happened to Rex (either way) I'm afraid you'd feel you got bad advice. But I will say that a very dear friend (human) had IBS and went to the doctor for over a year, ignoring my advice about the H.O.P.E diet (high fiber, omega 3's (fish oil), probiotics, digestive enzymes). He had numerous rounds of antibiotics, a colonoscopy and even an MRI. None of it resulted in an improved state of health. He was miserable.
Finally I just sent him the products so he started taking them. He felt better in a very short period of time and even now (a year later) will not go anywhere without them. He mentioned to me again recently how he can't believe that none of that other stuff helped but this has done the trick. I think he feels a little embarrassed that he ignored me for so long, but to be honest, I'm kinda used to it.
He has a Phd and is a smart guy - he asked them a lot of questions. But still drugs and surgery was what he ended up with. He wondered why his doctors didn't tell him about this. I have my BSN in Nursing and I know why they didn't tell him - we are not taught natural remedies. We are taught how to diagnose and then treat using mostly drugs or surgery. If you're a carpenter, every solution involves a hammer. No offense, it's just all we know unless we have challenged the status quo and taken the time and money to educate ourselves. (In which case, you can expect to be a little bit ostracized by your colleagues.)
If Rex is in critical or emergent condition and needs help right now, you will not find a better approach than drugs or surgery. Natural remedies generally take time. There are no guarantees in life but if you can wait, and support his Innate healing abilities, I think you will find a long lasting solution with only good side effects to the treatments.