I'm sorry to hear your kitty is not doing well.

I know that parsely is good for the kidneys. It is a natural diuretic (sp?). It makes the kidneys want to keep releasing urine, and acts as kind of a "flusher" of the urinary tract. Your cat will need lots of water though, because a side-effect is dehydration due to all of the peeing.

What type of food is he on? The quality of a food can definatly help.

Good luck!