Diesel at the vet. Not great prognosis so far.
$575 visit Monday. We left with ten days of antibiotics while we waited on two blood tests. Doc suspects he has kidney issues which may or may not be treatable. Also suspects possible thyroid problem (hence the second blood test). Diabetes which was our other possibility was ruled out (unfortunately since it's much easier to treat for than the kidney problem).
Tuesday morning, blood test results came back:
Thyroid problem? Check. Apparently one of the worst cases our vet has seen, this is the reason for his problems with his coat (you can see in the pic that his coat is very grey/brown instead of black as it used to be) and his lack of energy. Also most likely culprit for his loss of weight/muscle mass - from a high of 145lbs a couple years back (not fat) he is down to 118lbs today. Treatable with medication, full recovery expected.
Unfortunately, Kidney Problem - also check. The test does not indicate whether it is an infection, partial failure, or complete failure. If infection is the cause, the current course of antibiotics he is on should help and urine tests next week will give us an idea of whether or not he is improving. If so, he should be okay. If not, it's not treatable and his time is short.
More tests needed in a week to see how he responds to antibiotics. If good results he gets another ten days of antibiotics and a good chance at recovery. If not, kidney failure which is pretty much untreatable.