Laurie Anne Walden, DVM
The anal sacs, or anal glands, are a pair of small sacs located under the skin on each side of the anus of dogs and cats. These sacs contain smelly material that is normally squeezed out when an animal passes stool. If your dog is scooting his bottom across the floor, he might have an impacted (clogged) anal sac.
Anal Sac Anatomy
Anal sacs lie between the anal sphincter muscles, the circular muscles that close the anus. Each sac has a small duct that leads to an opening in the skin next to the anus. Anal sac material is liquid or pasty in consistency, ranges in color from cream to brown, and has a characteristic fishy odor.
The function of anal sacs is not entirely clear but might have to do with scent marking and communication.
Symptoms of Anal Sac Problems
Dogs and cats with anal sac disorders have symptoms of anal discomfort (these are more common in dogs):
Other problems, like parasites, fleas, and orthopedic pain, can cause some of the same symptoms.
Types of Anal Sac Disorders
The most common anal sac problem by far is impaction, in which an anal sac can’t empty on its own and material remains in the sac. Scooting the bottom on the floor and licking the anal area are typical symptoms. Impaction happens more often in small dogs than in large dogs or cats. The causes of impaction are not fully known. Many dogs go through their entire lives without ever having impacted anal sacs; others experience it regularly. Allergies, skin disease, and changes in stool consistency might make a dog more likely to have clogged anal sacs.
Impacted anal sacs can become inflamed, a condition called anal sacculitis. Anal sacculitis causes painful, swollen sacs and often redness of the skin around the anus.
Infected anal sacs can form abscesses. An anal sac abscess first appears as a painful swelling beside the anal opening. It may rupture through a skin wound that drains pus or blood next to the anus.
Anal gland tumors are less common than impaction, inflammation, or infection. They can cause swelling, bleeding, or discomfort in the anal area.
Veterinarians usually manage an impacted anal sac by gently expressing the material out of the sac. This process can be uncomfortable for the patient, especially if the material is too thick or dry to be easily removed. Some patients benefit from anal sac flushes or warm compresses applied to the anal area. Anal sac inflammation and infection are typically treated with antibiotics and pain relievers. The anal sacs can be surgically removed in patients with anal sac cancer or as a last resort for patients with other anal sac problems. (Surgical removal is not generally recommended for patients with simple anal sac impaction because of the possibility of complications after surgery.)
What You Should Do
If your dog or cat doesn’t have any symptoms of anal sac trouble and your veterinarian hasn’t found a problem, you don’t need to do anything in particular. There’s no need to change your pet’s diet or have the anal sacs expressed if they’re working normally. But be aware of the signs of anal sac impaction so you can have this uncomfortable problem taken care of before it becomes more painful for your pet.
Photo by Sheri Hooley
Laurie Anne Walden, DVM