Terri - keeping fingers and paws crossed - it is a v.distressing time for you but sounds as if your vet is being very thorough. Our cat(the one with cystitis) had X-Rays and an a bladder scan and kidney function tests as well as a precaution to rule out kidney stones etc. They have some pretty sophisticated techniques now. Hope the special diet does the trick. Let us know how you get on
Best wishes to you and Barnaby
Lynne and Paddy
