One of our cats, Baker, was transported to a 24-hour veterinarian's office by Mrs. Prof last night. For two straight days, we'd found kitty litter scattered all over the floor around the litter boxes (we have multiple, since we've got two cats). Last night, Mrs. Prof noticed Baker going back and forth between the litter boxes. She kind of spied on him using one of them, and noted that nothing came out. She felt his abdomen and got worried that he might have a urethral blockage, so off to the vet they went.
The good news was that there was no blockage. However, he might have been developing crystals. The vet couldn't tell since Baker's bladder was empty. So, conservatively, they gave him a pain med and medication to help relax his urethra. They also put him on prescription canned food. Meanwhile, Mrs. Prof needs to do some more research and consulting with her cat rescue friends.
As of this morning, Baker is still on the medicine. He's rather grogged out and assuming the pose of Meatloaf Cat on the floor. I've seen him use the litter box successfully, and he's not scattering the litter so much. He's not too enamored with the prescription food, but we'll deal with that. Time will tell how he progresses.