I'm so sorry, LM, but I, too, would wait to go all-in emotionally on the U vet's pre-imaging assessment. If he's only been on Gabapentin for less than a week, he could very well be getting used to it. I was told that it takes a *few weeks* for it to kick in and for the dog's pain signals get sorted out (you're basically changing the way his body responds to pain, which isn't as fast-acting as, say, NSAIDs)—and lethargy is definitely one of the side-effects. Especially if you're also doing Tramadol, it can be quite flattening, I think. Are you replacing the Tramadol w/Gabapentin over time, or is he meant to stay on both + the NSAID? (I'm just asking out of curiosity.)
Also, I've slowly learned to remember that, at least for MP, she may take a little longer to recover from an exertion, and progressively so, as she gets older (and that she keeps getting older at a faster rate than I am ready to process!)—I'd get super elated from a great park trip, and forget that she may be a little draggy afterward and become devastated when she's a little wobbly at home (she's always gimpier when not excited/ecstatic). Kind of rambling, but it's been a little of a rollercoaster for me, and every few weeks I end up a sliver short of despair, even though nothing has really changed and she is doing as well as she can.
If you'd want a second opinion, I love and trust our rehab vet in Burnsville with all my heart. No matter how busy she is, Dr. T has *always* been there for us, whether it was the holidays or the weekend or the middle of the night or she was out of the country at a conference, and even if it weren't entirely about her gimpiness. She's one of the only people in the world with some kind of special certifications/degrees (sorry for the lack of specificity; I just know that it was plenty bad-ass for me
), and is beyond kind and thorough.
Hang in there, LM! <3