Thanks for the additional info.
There are some fungal diseases that could lead to kidney failure. The best way to diagnose that, is with a urine antigen test. There is a lab called MiraVista that runs these fungal tests. I don't think the yeast on the skin or fungi is the underlying cause here, but it's worth ruling out.
My guess is that we're probably dealing with some type of chronic kidney failure. A urinalysis will help a lot. That will tell us if the kidneys are able to concentrate the urine. It'll also tell us if there is disease in the glomerulus- the filtration part of the kidneys. We see disease there by seeing protein loss into the urine. It just gives more information that it's true kidney failure and not elevated kidney enzymes from something else.
The leaking mammary glands does make me think of Pyometra as well. An ultrasound of the abdomen is done to rule out pyometra. We can potentially see secondary kidney failure from Pyometra. I wouldn't expect it to go on this long, but it's worth looking into.
I feel like there is a lot of jumping around with diagnostics and treatment here. There seems to be a treat and see what happens approach vs trying to get a diagnosis and treating specifically. If it hasn't been advised, a consult with an internal medicine specialist may be an option. They could at least get to a diagnosis so you know what you're dealing with and you know the prognosis.
When it comes to protein. I don't like to restrict protein in my kidney patients anymore. There is a new thinking that these dogs and cats are protein deficient as it is, so we shouldn't restrict them further. We should spend more time focusing on keeping them eating and increasing fluid intake. We shouldn't protein starve them, as they need all they can get to keep their weight on.
Keep me posted how things are going. If you can scan in the bloodwork, that would help a lot.