Ever wonder why your dog loves to rub his bum on your carpet? That's not just a strange dance, or even an unreachable itch — it may be that his anal sacs are full.
Anal sacs are small glands locate on either side of the tail. These sacs may be ½- to ¾-inch in diameter, with small ducts that empty halfway down along either side of the anus.
Anal sacs contain a foul smelling liquid that is usually ejected during defecation, but can also be released when the dog is excited (think "skunk"), or when his rectum is full. Anal sac contents may have served as an odoriferous message for wild animals, but these glands are not really necessary in our pets.
Most dogs never have problems with their anal sacs (although sometimes their owners have a problem with the smell!) but occasionally a dog will develop an impaction, and then the scooting begins.
Impacted anal sacs may feel like firm grapes on either side of the anus. If you squeeze the sac contents into a tissue (hint: wear rubber gloves so you don't get the stuff on you), the contents should normally be thin like oil or water. If the contents are pasty, it may mean the secretions are staying too long in the sacs and drying out.
Dogs that have anal sac impactions may need to have a diet change, so that they defecate more often (adding fiber might help) or so that the feces is larger and more firm and can therefore compress the anal sacs from the inside. Other dogs may have allergies or skin conditions that thicken the sacs and surrounding skin, making them more difficult to empty.
Dogs with impacted anal sacs may need to have the anal sacs manually expressed until they empty easily. This can be done from the outside, by placing a tissue across the anal opening and squeezing inward on both sides of the anus about 1 inch outside of the hairless area.
Most veterinarians will empty the sacs by inserting a gloved, lubricated finger into the dog's anus and squeezing each sac from the outside with the thumb. If the anal sac material looks thick or bloody, or the sacs are inflamed, your veterinarian may want to fill the sacs with a combination anti-inflammatory/antibiotic cream. If your dog has an infection of the anal sacs — particularly if the surrounding skin is red, thickened, or painful, oral antibiotics may be necessary to help resolve the infection.
Dogs with recurrent anal sac problems may need to see a dermatologist about allergies or other skin problems. Anal sacs can be removed surgically. An experienced veterinarian should perform the operation, since the nerves that control anal sphincter function (and therefore keep your dog continent) sit just behind the sacs.