The good news is, cats can recover fully from a blocked bladder, and as Catty mentioned, a food change will usually keep it from coming back. The vet will have to send his urine to check what kind of blockage it was (chemical or infectious) and will advise you on what to do next. You may need to give him antibiotics for a while, if it was an infection. If it was crystals, a new food will probably do the trick.

Generally, the longer you wait to take a cat to the vet, the more it costs when you actually do get them in. Cats are notorious stoics, and don't show pain until it's excruciating. I'm glad you saved your cat's life by getting him to the vet - but you can do your budget a favor in the future by doing it sooner if anything else goes wrong!

Love, columbine