Anal sac secretion is probably a way for cats to recognize each other but probably also a defense mechanism as in skunk. The contents of the anal sacs are normally emptied when the cat has a bowel movement or if it gets really scared.
The anal sacs are located on both sides of the anal opening. With a short narrow gait, they open into the anus and can be seen as two black dots. The anal sacs are glands that form a strong-smelling secretion with varying color and texture.
Cause
Overfilled anal sacs are common in cats. Heavily filled anal sacs can be seen or felt as small balls on either side of the anal opening. When the contents of the anal sacs become stagnant, infection can develop. Infection in the anal sacs can cause an abscess to form next to the anal opening, which can rupture if the anal sac is not emptied.
Symptoms
Common symptoms of problems with the anal sacs are that the cat scratches on the buttocks, licks or bites at the root of the tail or anal area. The secretions in the anal sacs can become bloody, purulent, grainy and viscous.
However, there are other diseases that can cause anal itching such as inflammation of the rectum as well as pure behavioral disorders with anal licking.
Treatment by a veterinarian
In case of overfilled anal sacs or blockage in the canal to the anus, the cat needs help to empty and flush the contents out of the anal sacs.
The procedure can usually be performed on an awake cat, but in severe pain, sedation and pain relief may need to be given. If the cat has repeated serious problems, the anal sacs can be removed surgically.