Cat IBD diagnosis, but treatments aren't working. What else could it be?

Hello, and thank you for using Petco Pet Education Center, formerly Petcoach. I'm sorry to hear about Portifoy's diarrhea troubles! It's not clear from the history what sort of duration we're talking about, but it can take time (sometimes weeks) to get IBD symptoms under control. Many cats improve much faster if put on a tapering dose of steroids (often prednisolone is used), so you could talk to your vet about this. Depending on what diagnostics were performed that led to the IBD diagnosis, those symptoms could indicate IBD, but could also be consistent with a food sensitivity/allergy, or GI lymphoma, among other things. An abdominal ultrasound helps with a diagnosis, if that hasn't been done, with a GI biopsy being the ideal diagnostic (although that's also quite invasive, and your vet can help you decide if it's worth the risk).

At this point, I'd recommend communicating with your vet and letting them know how Port's doing, as they may have been hoping his symptoms would improve with the medications you mentioned - but they may want to change things (such as adding a steroid, or discussing the next diagnostic step) once they know he's still having diarrhea. Feel free to request a consultation if you'd like to discuss Port's case in more detail. I hope this helps!