My 3 year old male cat has been licking his rear end a few times a day for
about a month.  He does not have long hair and I do not see any feces stuck
to him which would require extra cleaning.  He uses the litter box just fine,
he was fixed as soon as he was old enough, his appetite is good if not a
little excessive, he is playful and alert, and my female cat is NOT having
the same problem (so I doubt he has worms).  He has had crystals in his urine
and so is on a permanent diet of Prescription Diet C/D canned food, the C/D
dry food and most cat treats make him vomit all over my carpet.  When he had
his last major episode of urine blockage, he had been licking his male parts,
so I have been vigilant to make sure he is not having a relapse.  

This morning, I saw him drag his rear across the carpet much to the glee of
my female cat who spent the next several minutes investigating the location.
I think maybe he has a clogged scent gland?  The vet did not seem too
concerned on the phone this morning and offered me an appointment in a week
or so.  Anyone have any suggestions, or disagree with waiting a week for the
vet to take a look at him?