I have a male cat. 8 years old. neutered. slightly overweight. Sometimes he makes very loud and deep meow noises, it's almost like a howl. It can only be described as 'aaauuUU' with a very heavily accented 'U'. He's had kidney stones before but he doesn't seem to be in pain. He only does it out of sight and stops right away if you catch him doing it. Other than that he's fine and very charismatic. Sound familiar to anyone?