He has one kidney much smaller than the other, with a possible stone. Plus
elevated urea and creatinine levels, though not critical.
He is also anemic...PCV of 20
I do like this vet. He's investigating many avenues, talking to the people
in pathology. It may be that his kidney isn't releasing the hormone to
create red blood cells. They're going to culture his urine, if I can get
him to the vet before he has his morning visit to the litterbox (not likely,
since they only open at 10:00 am on a Saturday!)
he's kind of holding his right paw out at times. But if he had an
infection, wouldn't he have a fever?
Toni

If his urea and creatine are elevated, it's a good idea to check his
blood pH. If the pH is low (7.8), you need to fix that urgently.
Lower blood pH causes protein catabolism (elevating urea) and bone
dissolution - probably interfering with production of new red blood
cells (anemia) and increasing mineral load on kidneys. Are his blood
levels of calcium and phosphorus within normal range? Most feeds today
are acidified to prevent struvites. So you'd need to switch him to a
neutral food like a kidney diet or a canned diet that is not acidified
(IMO, canned is a must for CRF, ARF (acute RF), or a cat with history
of uroliths). What are you feeding him now?

You did not mention if you are giving him any meds. Some meds can
cause ARF or anemia. Has he been holding out his right paw at times
since he became lethargic? Has the vet examined his paw or x-rayed it?
Does he limp when he walks? The lethargy may be primarily because of
the paw - he may be feeling more pain than he shows.

I found a very nice text discussing feline anemia and possible causes.
It's at
http://www.drpetra.com/Cats/Anemia%20in%20Cats.htm

I believe you took him in again today. Any news?