Blood tests and urine test - different results - puzzle

I don’t know whether anyone has experienced this or can shed any light.
My retriever was due to go in to have a small lump biopsy and due to her age (11) they took bloods before sedation, one marker was elevated so they sent the bloods to the lab. In the meantime I collected a urine sample, which was dilute, as was a second one - I’ve taken another in from her first wee this morning and am waiting for the results. She is drinking and weeing normally. The vet doesn’t want to sedate until has ensured all is ok.
If the bloods came back ok for kidney then what could be cause of dilute urine? She is fed commercial raw - and I did wonder if the increased fluid in this could result in dilute urine.
Any ideas/thoughts/experiences?
Just had results from thsi morning’s sample and it was still dilute, not as much as later in day ones, but the vet doesn’t really know. She has said it is possibly early signs of kidney issues - and she could take 3 samples in a row if I want, to send to the lab as they might pick up protein she hasn’t. Surely blood tests are more accurate than urine samples? Is there anything else this could be?

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.

Thanks for the reply.
So far I have handed in 3 urine tests - 2 in afternoon and today’s first thing - the latter not as dilute, but still dilute.
Before the byopsy the vet took bloods and one marker was slightly raised - to do with kidneys, so she sent the bloods off to the lab for more detailed analysis - these came back fine and no issues. What has muddied the waters is the urine tests - done three times and all dilute.

I always thought blood tests were the more informative, so if kidneys are showing as fine on blood results from the lab, what else could be causing dilute urine? She has said that the only other test would be to look at protein levels - even though dip stick showed no protein - so take 3 samples over a period of days and send them off to the lab to look at renal function again… At the moment, the vets are very busy and having a conversation is not easy.