Cats have anal sacs also but the secretions are much more putty-like than the dog's more liquid and odorous type. Often when cats are having a bowel movement or straining in some way, the small projections on each side of the anus (the opening of the anal sacs) may protrude slightly, then flatten back down to normal when the episode has stopped.

Anal sacs are thought to be remnants of modified scent glands much like the scent glands in a skunk. The skunk's scent glands are more developed for spraying, but when dogs get excited, nervous, or scared, they can "squirt" or leak material from the anal sacs that has a very foul odor. You may have noticed such an odor and were not aware of its source.

The anal area should always be checked during a physical examination and the anal sacs expressed or "squeezed" if they are distended. It is important to allow a veterinarian or other trained professional to perform this task since it is easy to bruise the small delicate muscles that surround the anal sacs.

The fluid from the anal sacs should be dark brown to medium brown. If yellow color and/or blood is seen in the fluid an inflammation or infection may be present in the anal sacs. Flushing of the anal sacs with anti-bacterial preparations and then filling the sacs with antibiotics are the treatment of choice. If the infection recurs more than two-three times surgical removal of the anal sacs should be discussed.