The cat may just have overactive thyroid. Very common in cats. Easily handled with meds heck science diet makes a rx food to treat thyroid issues.
Even if it is kidney I have known cats who live years and years with easy to administer treatment.
I am a licensed Vet Tech. I just don't work in my field due to child care issues.
40 yo straight female
Married in the eyes of the government to Butch since 2001...
Murf my monogamous second husband has been with me since May of 2012.
In a V relationship with an average 60/40 split of time. Only due to Murf's and Butch's crappy work schedules.