Duffy refused to use the nosorb litter the 2nd time I tried it. Unless you use several containers of nosorb or have the box tilted & the cat stands on the higher side they just end up stepping in their pee anyways.
If you can get a first of the morning appt & lock Sam up in a room without a litterbox for a couple of hours prior, hopefully you can get him in to the clinic with enough in his bladder for a sample, providing he doesn't pee on the way there.
Avoid biting when a simple growl will do
The Spirit Lives As Long As Someone Who Lives Remembers You - Navaho Saying
Vindication ~ For all those pets who became sick or lost their lives from tainted pet food