I got a call from the vet.
They gave him a shot of something to relax his urethra. He was able to pee a little this afternoon, but not anymore. The vet can empty his bladder by squeezing it, but it's not a solid stream. She said his bladder isn't as firm as before, which is good. They're going to give him the drug again and leave it over night. If, by morning, he is not doing well then they will cath him again.
If there is a god, then please, please help my boy!