My 15 year old lemon hound pees four to five times more than normal and has been for over a year. Been tested many times for bladder infections, kidney issues, and other normal things. The pee is as clear as water and can have strong ammonia smell at times. She drinks a lot but vets have told us to make sure she has water available at all times. Other that aches and pains from arthritis, she seems not to have any other issues. Any ideas of rare conditions that may be causing to peeing trouble?

Thanks,
Bubba