What are the anal sacs?The anal sacs are two small pouches located on either side of the anus at approximately four o'clock and eight o'clock positions. The walls of the sac are lined with a large number of sebaceous (sweat) glands that produce a foul-smelling fluid. The fluid is stored in the anal sacs and is released through a small duct or canal that opens just inside the anus. The anal sacs are commonly called 'anal glands'. They are present in both male and female cats.
What is their function?The anal sac secretion contains chemicals that act as territorial markers, or 'catcalling cards'. The secretions are similar to those produced by a skunk, which are used to repel enemies and alert other animals to their presence. Although cats can use their anal sacs for the same purpose, most domestic cats have no need to repel predators in this manner. A small amount of anal fluid is usually squeezed out by muscular contractions whenever the cat passes a bowel movement, providing a distinctive odor (or individual 'scent signature') to the feces.
What diseases affect the anal sacs?The anal sacs or their ducts can become inflamed or infected due to a variety of causes. If the anal sac ducts become swollen, the fluid cannot be emptied properly from the sacs during defecation. In this situation, the sacs may become impacted (plugged) and the fluid becomes thicker and darker in color.
"The anal sacs or their ducts can become inflamed or infected due to a variety of causes."
Bacteria that are normally present in the feces can readily travel up the ducts and enter the sacs. In normal situations, the bacteria are flushed out when the secretions are expelled during a bowel movement. However, if the sacs are impacted, the fluid does not empty normally and the impacted fluid provides an ideal medium for bacterial growth. If the anal sacs become infected in this manner, the fluid becomes bloody and eventually, the sacs become filled with pus, forming an anal sac abscess. Anal sac abscesses are hot, painful swellings that can occur on one or both sides of the rectum. Left untreated, the pressure will continue to build until eventually the overlying skin bursts open, allowing the pus to drain out in a condition called an anal sac rupture. The pus can then spread into the surrounding tissues and cause severe damage to the rectum and anus.
Another cause of recurrent anal sac disease is a change in stool consistency. This can occur in cats with food allergies, inflammatory bowel disease, constipation, and megacolon.
What are the clinical signs of anal sac disease?Signs of anal sac disease depend on the nature and severity of the problem. The first signs include scooting or dragging the anal area along the ground and licking or biting at the rectum or the tail. Anal sac disease is very painful and even a normally gentle cat may scratch or bite if you attempt to look at the affected area. If one or both anal sacs become abscessed, the area beside the rectum may be swollen. If the abscess ruptures, you will see a bloody or sticky discharge draining beside or beneath the rectum.
How is anal sac disease treated?The treatment for impaction is to express the sacs and flush out the solidified material. Infusing the affected sac with anti-inflammatory and antibiotic drugs may also be required. For infection, the sacs must be expressed and antibiotics administered orally to the cat in order to kill the bacteria. Most cats will respond well to pain relief medications and antibiotics (e.g., clindamycin, brand names Antirobe®, Cleocin®) that are prescribed for several days until the swelling and inflammation have subsided. If the anal sacs abscess or rupture, surgical treatment may be necessary.
Is the condition likely to recur?It is not very common for cats to have recurrent anal sac disease. However, some overweight cats may develop chronic anal sac problems. It has been observed that the anal sacs of many obese cats do not empty well, thus these cats may be predisposed to recurrent anal sac problems.
"It is not very common for cats to have recurrent anal sac disease."
If the cause of anal sac disease is change in stool consistency, prevention involves treating the underlying cause and may require changing the cat to a higher fiber diet. If a cat has several episodes of anal sac disease, and diet or supplements do not relieve the problem, the anal sacs can be removed surgically.
What are the potential complications of surgery?Surgery requires general anesthesia, which always carries some degree of risk, whether the patient is a cat or a person. Removal of the anal sacs is a delicate and specialized surgery. Some veterinarians may refer these patients to a board-certified surgeon.
Some cats will experience lack of bowel control after the surgery. They may drop fecal balls while walking or experience fecal incontinence when they sleep or lie down. This occurs because the nerves that control the muscles surrounding the anus are located near the anal sacs and may sustain minor damage during the removal of the anal sacs or become inflamed as part of the post-operative healing process. In most cases, this is a temporary problem that will resolve within a few days to a few weeks after surgery. Unfortunately, some rare cases never improve, resulting in the need for special diapers or other accommodations for fecal incontinence. Your veterinarian will thoroughly discuss the risks and benefits of surgery with you.
What other problems can develop with the anal sacs?Older cats can develop cancer of the glands in the anal sacs called adenocarcinoma. Therefore, it is very important to have your cat examined by a veterinary as soon as any of the above clinical signs are seen.

This client information sheet is based on material written by Tammy Hunter, DVM; Ernest Ward, DVM© Copyright 2018 LifeLearn Inc. Used and/or modified with permission under license.