Hello. What was the marker that was elevated? Was it one that pertained to renal function? Just like in humans, one of the functions of the kidney is to concentrate urine and this, along with your dog’s age is probably why the vet is hedging her bets. There is also metabolic factors with a role to play in the concentration of urine.
I suspect that variation in urine concentration is quite normal through the day. Again, this is just the same as humans - we drink a bit more, it’s colder weather so we don’t perspire so much and we then have paler urine.
I can’t remember the exact figures, and they vary anyway but a high percentage of raw and wet food is water so the urine will be more dilute unless he’s not been out for a wee for a good while.
Regarding the blood tests, I can only speak from a pet owner’s view. Most of the blood tests that my dogs have had were done in house. However, some have had to be sent off to the laboratory for more sensitive testing. Most recently these were hormone tests.
How you proceed is up to you. Having the three consecutive blood tests would give you peace of mind if they come back normal. However, there may be nothing to worry about. He hasn’t any other glaringly obvious signs of renal disease. It could just be due to his age and older dogs can go on for some years - kidney disease is sometimes slow in development.
I hope that your dog is able to have his biopsy and that the result is one that you hope for.