Hello & welcome, Emma. I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now as I am sure you can appreciate, blood in the urine is not a normal finding. As well, it is not a common finding for kidney disease alone. Therefore, we'd not assume this was just related to her reduced kidney dysfunction and the lack of bacteria make infection less likely (though if they took the urine after the antibiotics this could be a false negative). Therefore, we'd have to be wary of stress induced cystitis, bladder stones, bladder tumors, and urine crystal issues (though we'd have hoped this would have been checked for on her urine test, so you may want to double check that). As well, though less common we can see infections in the kidney as well as stones and tumors that could also cause the signs you have reported.
With this all in mind, her situation is a tricky one. With the blood raising these additional concerns, it would not be advisable to just treat for kidney disease and hope for the best. Especially as ultrasounds are not invasive and many cats allow them to be done without any sedation. The only part that cats tend to mind is having a little belly shave beforehand. As well, you don't have to actually starve her, but just stop food at bedtime and skip breakfast until she is scanned. You could even request that her vet do her scan first thing, so that you can feed her afterwards if you are worried.
Still, if you are not keen, you could speak to her vet about trialing supportive care. If you choose to go down this route, I would strongly advise making sure they send a urine sample to the lab to be checked for crystals and any sign of bladder tumor cells (just to try and reduce those concerns). As well, the lab specialists will be able to check for material in the urine (casts) from the kidneys to give us a hint of that is where the problem lies. And that could give us some more clues to the root cause we need to address for her. As well, if you do choose this route, a kidney friendly diet (that is low sodium/protein/phosphorus) can be started but you may also want to have her vet ruling out stress cystitis for her using supportive treatments like (ie cystaid, cystease) +/- using a kidney supportive drug (ie Semintra, Azodyl) to ensure optimum function for her.
Overall, ultrasounds are not invasive and most cats aren't bothered to have them. So, if she is still passing blood despite their treatment, it would be the best next step here. Otherwise, you can choose to hold off but if you do, then a full urinalysis and the above treatments should be considered to rule out as much as can and ensure we are addressing any of those issues that may be present for Daisy.
Please take care,
If you have any other questions, please ask me – I’ll be happy to respond.
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You are very welcome,
I am glad to hear that they did have it checked at the lab to try to rule out those other concerns. Still, as those have not allowed them to pinpoint the cause for Daisy's signs, I do think it is best to have the scan. That way we will know what we are facing and can ensure we address it as effectively as possible for her. And I'd note that you could perhaps even see if they will allow you to stay with her, if you think that may reduce her stress in having to visit the vet for the ultrasound.
You are very welcome, my dear. :)
I am glad I could give you peace of mind and wish you both the best,