I don't know of many vets who would, this would be extremely unethical!

Seren, the bloods and urinalysis would be a good starting point. At least this way there is some indication as to what is happening, and then (if necessary) ultrasound etc but bloods/urine are most important. Depending on the results there is medication available, but would also be worth changing the diet onto a lower protein/phosphorous as this will help the kidneys too.