My cat Cody went through this problem many years ago when he was only 2. He had such a bad case of crystals that he was hospitalized over Thanksgiving, again just before Christmas, and then right after New Years. His special diet wasn't working so the vet advised that he have an operation. He snipped off Cody's penis to enlarge the hole for the crystals to come out. The operation wasn't too bad. Cody recovered quickly and he never had a problem with crystal blockage again. He didn't even need special food. Just wanted to let you know of the alternative, if needed. The operation was well worth the money because I had Cody for an extra 13 years.

Diane
Mom to Gracie and Ally
and my angel Cody