Walter and Nimzo are domestic short hair cats, brothers from the same litter, aged nine. Walter is a grey tabby and Nimzo is black with the tiniest patch of white on his tummy. We all live in London, England. On reflection, I should have known there was something wrong before as both cats have always drunk a lot of water but the urination had increased dramatically and it was like chipping out concrete when it came to cleaning the litter tray. Hindsight is a wonderful thing!