My cat had ash crystals build up in his urinary tract and it almost killed him. The vet said that he was lucky to have made it. (I waited a couple days.)
He said this is common in neutered males and comes from eating "cheap" catfood- Meow Mix is what he was eating. So then I had to start buying this horribly expensive catfood. (It was like $45 a bag but it dissolved the ash.)
I would probably bring him in.
(I sent my husband to the vet with my cat once while I was in tears b/c I thought he was dying and they would put him down. I knew I couldn't handle it so I asked my husband to do it for me. Turned out he was constipated. I felt silly, but SO relieved.)