Royal Canin/Control Formula/kidney problems

My Cat Buddy had UTI but that cleared up but then I had another test done and it showed there were bacteria but no crystals. I had gone to another vet to get a second opinion with the tests but not the cat. She said it could have been a false positive to possibly redo it. Meanwhile she gave me the Royal Canin Vet Diet Control Formula in wet and dry. this was August 2008. Buddy loved the dry but not the wet so after a month or so I noticed he started to drink more water I went back to the second vet to get another bag as I thought it was good for him and I asked the vet does this food make him drink more water, she said yes. Well he started drinking gobs of water and peeing a lot so I took him off it but it continued until he passed away yesterday. Is this a coincidence or I began thinking could the food have made him worse. His kidney signs from blood were okay in Feb with 2 off a notch then when he got very ill a few weeks ago his blood tests were awful. Kidney disease 85% kidneys gone. We did test the bacteria and did a culture and sensitivity in dec and he had lots of bacteria in rods and was put on meds and all cleared up. I just thought it odd that he began drinking so much water with this food. Its all too late now but its always been in the back of my mind, especially now!!