Hello, I'm Dr. Deb.
I recently came online and see that your question about Milo hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
What an absolutely horrible experience for you both! And, for Milo still to be ill is even worse, isn't it?
I have several thoughts as to what may be causing his symptoms which I'll list below. I suspect his change in personality at home is because he just doesn't feel at all well. I believe that's why he's hiding, too.
1. Despite normal blood work and x-rays, he could have an obstruction or a foreign body; in other words, he ate something he shouldn't have which is now lodged in his stomach or intestines.
X-rays aren't always definitive in such situations since objects such as sponges or fabric , etc. won't be seen. An obstructive pattern in the intestines may be suggestive of such a problem but usually additional testing such as a barium study or ultrasound are needed.
If he is obstructed, then he'll probably need surgery to remove whatever it is that he ate.
2. About 30% of cats with pancreatitis will vomit; they typically don't want to eat and may become reclusive. The blood work that was done rules out many conditions but it doesn't rule all of them out such as pancreatitis. We often have to request that a special pancreatitis test be done which can help confirm the diagnosis.
Treatment is primarily supportive which means we keep the patient hydrated, control the vomiting with medication and provide pain control (we think pain is why these cats behave as they do).
Given Milo's extreme dislike of vets, it's definitely going to be a challenge to try and determine what might be going on with him. If a pancreatitis test wasn't requested, your vet can ask that it be 'added-on' to the previous tests done since they already have his blood.
If the number is ***** then at least we have a provisional diagnosis. Treating him, however, is not going to be easy; however, having said that, Milo isn't the first cat (nor will he be the last) who becomes aggressive at a vet's office. If your vet feels intimidated by him, then perhaps it might be best to take him to another vet. The blood test results and x-rays can be shared with them.
I do have one suggestion which may help with his nausea: over the counter Pepcid AC (Famotidine) can be given at a dose of 1/4th of a 10 mg tablet twice a day. I'd crush the tablet, mix it with a very small amount of water in a syringe and squirt it into the side of his mouth. I'd normally suggest that you put the pill in canned food but since he's not eating and still nauseous, this obviously is not a method which will work.
I share your concern about Milo since if he only had a simple "gastritis", I'd have expected him to have responded to your vet's treatment. I also wouldn't have expected him to be behaving as you're seeing. In my opinion, something else potentially more serious is going on with him....although I wish I didn't think this:(
But, I hope this helps to at least provide additional options for you to consider and possible explanations for his symptoms.
Again, my profuse apologies for the delayed reply. Deb