Despite her love of your couch, your cat has many of her natural tools for living life in the wild, including her anal sacs. When your cat poops, a bit of this funky substance comes out as well, giving her waste its own distinct odor. Occasionally a cat may have some trouble with her anal sacs and they become impacted, inflamed or infected. You can give your cat some comfort from inflamed anal sacs. A warm compress will soothe her irritated hind end and soften the contents of her anal sacs, making them easier to express.
A Home Remedy for Anal Sacs in Cats
Anal gland - Wikipedia
However, sometimes her bum gets red and inflamed making her scoot and scratch; what a bummer. Several culprits may be responsible for her unwelcome public suffering. Dry cat food is notoriously, well, dry. Defecating becomes harder, in every sense of the word, when your kitty is dehydrated. This can irritate her bottom. This rehydration may be all she needs in order to solve her bottom problem.
Cats anus is slightly swollen but definitely not prolapsed yet, what should we do?
The anal glands or anal sacs are small glands near the anus in many mammals , including dogs  and cats. They are paired sacs on either side of the anus between the external and internal sphincter muscles. Sebaceous glands within the lining secrete a liquid that is used for identification of members within a species.
Pet's info: Cat Devon Rex Female spayed 6 years and 7 months old. She may have an anal sac infection or abscess. Since she is in pain, it would be better if you could take her in to a Pet ER before Monday, but if this is not possible you can put some vaseline on You may want to offer your Pet a diet of soft foods to help minimize irritation to the gums.