Sad ping.
I just lost my last grrey kitty last Dec to renal failure.It is not something you are going to want to extend her life for as it is very painful for the cat.Mine came on quickly and he was just short of his 10th birthday.You need to find out how much loss she/he has, anything over 70% and you are only going to make their suffering worse. I am sorry.By the time we found out ours had it he was in the over 80% failure range and started retching that foul stuff up and wouldn’t eat.We decided as much as we loved him I couldn’t force him to stay that way and we decided to put him down.