Sorry to hear that Muddy has something like that. I'm not familiar with that one by name. Most of the ones we see at work are more of a head tilt which is a different thing. I did google it and some findings suggest that regular disk problems may be misdiagnosed as DM by xray alone, and suggest an MRI, although I'm not sure how much different the treatment would be.

The Metacam would help the arthritis, however with elevated BUN & Creatinie levels it would not be as safe. Any NSAID can cause problems with already elevated levels of liver and kidneys. However maybe your vet can give you some Dasaquin or something similar that may help a bit without being as damaging to the organs.

I hope Muddy's coughing stops soon and at least has one less thing to bother him. Hopefully Muddy's vet will find a treatment that works for him. Thank you for posting an update.