Anal sacs -- sometimes called anal glands although they aren't glands by definition -- are small pouches between the inner and outer anal sphincter muscles. They're at 4 o'clock and 8 o'clock outside the anus, and may be exposed by gently pulling down the skin at the bottom of the anus. Dogs' anal sacs produce a potent, foul-smelling brownish liquid used for territory marking and individual identification. Some pets produce thicker anal sac fluids, increasing the risk of impactions and infections.
The usual cause of an anal sac infection is inflammation in the duct through which the anal sac fluid drains. When the duct's passageway swells and narrows, fluid doesn't drain as efficiently as it should. Thicker fluid is more likely to stop properly draining, which is why pets with more runny fluid are less prone to impaction. The anal sac fluid is an ideal environment for bacterial growth, and abscesses form readily. Underlying conditions, such as enlarged anal sacs, a naturally narrow anal sac duct, excess weight, and anal sphincter muscle dysfunction sometimes contribute to anal sac infections. Small breeds are more susceptible to anal sac problems.
An infected anal sac becomes inflamed and produces discomfort, itching or pain in your pet. Anal secretions are thin and yellowish, and sometimes contain traces of blood. Your pet may experience pain while passing stool. She's may scoot her rear along the floor or lick or bite at her anus frequently. Fever and red to purple discoloration around the area often accompany an abscess, which will have discharge if it ruptures.
See your vet if you suspect your pet has an anal sac impaction or infection. He'll probably start by manually draining, or expressing, the anal sacs, and he'll show you how to do it at home when necessary. Abscesses may also require manual drainage. Antibiotics help resolve many infections, as well; sometimes the anal sacs are infused with antibiotics directly in addition to the administration of an oral antibiotic. Your vet may suggest increased dietary fiber intake or a laxative until your pet begins passing stool normally again.
Untreated anal sac impactions and infections can cause ruptured anal sacs. When left unchecked, infections can spread to other areas of the body; additionally, your pet can contract an oral infection or develop tonsillitis as a result of licking the infected area. Pets with increased susceptibility often experience recurring impactions, infections or abscesses. Surgical removal of the anal sacs is commonly recommended.