First off, I really really like Dora, the monkey and your cat! Reminds me of my Maddie and Zack!
First lets go through our assumptions: things we will assume to be true unless proven otherwise (this is how vets often think). He is an outdoor cat, so I'm gonna assume there is no Feline leukemia, FIV (http://www.iwillhelpyourcat.com/videos/#/fiv-cats/) or FIP going on. This is a fair assumption but is worthwhile double checking with your vet or testing for (via a blood test you can request).
Second assumption is that with all his hunting, that there are no internal parasitic infections going on. Not that is likely to be a main problem, but a simple application of dewormer (that takes care of tapeworms and protozoal parasites) cleans the slate, takes away some of the guesswork, and eliminates cumulative internal stress (i.e. something that is just adding to the monkey on his back…except for the cute one while he is sitting on that Dora couch).
There is something that I call “skinny back”. There are expaxial muscles, fat stores and connective tissue over the lower back. Since Im not an anatomist, and neither are my clients, I just call it skinny back. This area of the body is smaller than it should be.
When I see skinny back in a cat, Im assuming this patient is trying to tell us something. I see this on a weekly basis, which tells you how common this situation is. A cat could have a skinny back and otherwise behave and act normally on the outside (yet something is truly going on health wise). Sometimes they have that skinny back and they are actually showing outward signs of problems. Once in a while I meet a cat who has just always looked like that (but they still drop body mass in that location, so it’s just harder to tell). For those cats who have aspirations to be runway models, yes, you can have a skinny frame and be totally normal.
What I can tell you is that if a cat has that skinny look to their back, I make the assumption that this cat is speaking to us. Your cat is saying “hey, lets find out what is going on - maybe im just skinny, but maybe there is some requirement i need and I'm missing it from my life”. Skinny back is non-specific - It can be a subtle age related thing, like progressing arthritis, nutritional, all the way to early stages of “metabolic” illnesses.
So, whats the implication here for Andrea's cat?
Her cat is lanky but petite all at the same time. From what I can see from the photo, he has skinny back. So Andrea is very correct is trusting her gut, and thinking “Am I missing something here? I don't want to miss something until it’s too late”.
His bloodwork initially came back normal. When you are a small cat, with smaller reserves of fat or muscle mass, normal test results on bloodwork can be misleading. You need lots of muscle mass to produce creatinine for it to show up on bloodwork. I’ve seen cats with significant CKD (chronic kidney disease) that show up empty with their creatinine. There are new tools to help with this (SDMA test - more on that in an upcoming blog post).
So for these guys, I do what I call my “minimum database”. I need a better name for it. But the minimum part implies that even though Im asking a person to do x, y and z, it really is the minimum to ensure Im not missing something (other than they physical exam, which is really the most important). Im looking at a repeat of blood, urine, and an X-ray.
Im repeating the blood, and looking for “grey zone hyperthyroid”. These are cat’s who don't read the book. There initial thyroid screening comes back normal but they are in fact not. Something is suppressing their thyroid, therefor masking it, or you need to run a different type of thyroid test to show it up. Show me a google search with a description for a cats illness, and I can show you a cat who didn't bother to read it and yet truly have that problem. So I wont expect them to show any classic signs of hyperthyroidism whatsoever. Except for that skinny back…
By repeating the blood, I'm also looking for trends. Even things that are within normal range…I'm trending it. Sometimes the devil is in the details.
Im doing a urinalysis and protein creatinine ratio on that pee. Maybe a culture. Maybe not. Depends on the persons budget and I have a love / hate relationship with urine cultures.
Im always going to X-ray them as well. As a vet, you only need that 1st experience in which you have failed someone because you did the bloodwork, urine, everything looks great (except the cat or dog), you want to save someone some money, so you don’t emphasize the X-rays, and there is the answer all along…ugh.
That’s how I would begin. And there is a chance that we reveal that one thing that her cat needed, and he’s grateful for it! Or that he is an older sleepy dude…and he’s grateful that we didn't chance on missing something that would have shortened his years!
Hope that gets you started,