the same thing has just happened to Sadie, crystals and all, 3 lots of antibiotics over 3 weeks and she seems fine now. Apparently the worry is that although it may start as a simple cystitis, the infection can travel up to the kidneys and that's not good. Also crystals eventually can form bladder stones, and that was our Vet's main concern. Anyway, antibiotics have settled Sadie down, we just have to keep an eye on her. So Louis should be fine, all the best to him