Is your cat licking this area a lot, and hiding away? My cat had a ruptured anal gland which looked alot like the picture (only larger) and she was constantly licking it and hiding in the closet. She needed antibiotics and they needed to clean out the area and had us apply warm compresses and a special ointment to it several times a day. Not knowing exactly what it is or how your cat is reacting to it, I suppose you could try applying warm compresses to it to draw out as much infection as possible until you get in to see a Vet.
That is good. But what did the vet think it was due to?
I can't remember the exact terminology I guess it's just the genetics of the breed they said something like if theirs too much food the anal glands can't be pushed out so it clogs up in their system. I wanted to do a flush but buddy $300 I'll have to look at other options. Other than that they saw no other concerns to mention possible full Siamese breed also
