Anal Sac Disease
This information is not meant to be a substitute for veterinary care.
Always follow the instructions provided by your veterinarian.
When your dog scoots its rear end across the floor it most likely isn’t due
to worms. Dogs scoot when their anal sacs are uncomfortable. Anal glands and
anal sacs are part of normal canine anatomy. Every canid from wolves to
Chihuahuas have them.
Anatomy of the anal sacs
Anal glands are scent glands located around a dog’s anus, which produce a
strong-smelling, oily secretion. Anal sacs are located between the internal
and external anal sphincters (sphincters are the muscles that allow the dog
to keep stool in the rectum until it is time to pass) and store this
secretion for territory marking. The anal sacs empty through 2 openings
located on either side of the dog’s anus. When the anus is stretched as
stool is passed, the sphincter muscles squeeze the anal sacs and force the
contents onto the surface of the stool.
When dogs greet each other with familiar sniffing, the secretion from the
anal glands is what they are smelling. Anal sacs vary in size based on the
breed of dog Obviously, a St. Bernard will have larger anal sacs than a
Pomeranian, but generally healthy anal sacs range in size from a pea to a
kidney bean. Problems occur when the sacs get too full and impacted. If the
contents of the anal sacs are not emptied on a regular basis during the act
of passing stool, the normally liquid contents become very thick and plug
the openings of the anal sacs. The impacted glands can cause discomfort or
worse they can get infected resulting in an abscess. Fluid from a normal
anal sac does NOT have a pleasant smell, but if infected the smell can be
To ensure that the anal sacs are emptying properly, have them checked on
a regular basis. This is a simple and painless procedure that should be
included in a complete physical exam. If the glands are full they can be
easily emptied while the contents are still fluid. It becomes more difficult
to empty the anal sacs when the contents begin to thicken.
If you are unsure if your dog needs their anal sacs emptied, watch their
behavior. Dogs with impacted anal glands will often scoot their rump, or
they may look, lick, and/or bite at their anus. What predisposes some dogs
to anal sac abscesses is unknown. Dogs that are very obese tend to have more
problems than physically fit dogs. This may be due to fat skin folds
blocking the pores and preventing them from draining; or because it’s
difficult for the obese dog to groom itself and encourage natural drainage.
If your dog repeatedly develops anal sac abscesses the sacs can be removed
Anal glands and anal sacs are not usually discussed when people talk
about their pets. They are however a part of your dog and as a responsible
owner its your job to recognize when your dog is having a problem. Early
treatment is best and avoiding an abscess will make you and your dog much
This Pet Health Topic was written by Sarah Hoggan, Washington
State University, Class of 2001.
Washington State University assumes no liability for injury to
you or your pet incurred by following these descriptions or procedures.
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