Anal Sac Disease in Cats

By Malcolm Weir, DVM, MSc, MPH; Tammy Hunter, DVM; Ernest Ward, DVM


What are the anal sacs?

The anal sacs are two small pouches located on either side of the anus at approximately the 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. This fluid is stored in the anal sacs and is released through a small duct that opens just inside the anus. The anal sacs are commonly referred to as '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 'cat calling cards'. The secretion is similar to that produced by a skunk, which is 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 'scent signature') to the feces.

What diseases affect the anal sacs?

The anal sacs and 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.

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 the overlying skin eventually 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.

"Anal sac abscesses are hot, painful swellings that can occur on one or both sides of the rectum."

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 are scooting or dragging the anal area along the ground and licking or biting at the rectum or the tail. Affected cats may also show hair loss around the base of the tail or on the belly which is secondary to excessive grooming. Reluctance to defecate may also occur.

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 medication may also be required. Because this can be painful, treatment may require sedation.

For infection, the sacs must be expressed, and oral antibiotics must be administered to kill the bacteria. Most cats will respond well to pain relief medications and antibiotics, such as amoxicillin-clavulanic acid (Clavamox®) or clindamycin (Antirobe®), that are prescribed for several days until the swelling and inflammation have subsided. Your veterinarian may also recommend using warm compresses for additional pain relief.

Your veterinarian will let you know when your cat should be reassessed. This reassessment will likely include expressing the anal glands again and may require a repeat infusion of anti-inflammatory and antibiotic medication.

If the anal sacs are abscessed but have not ruptured, surgical treatment to lance the abscess may be necessary.

Is the condition likely to recur?

It is not very common for cats to have recurrent anal sac disease, but this can be seen in cats with obesity, chronic diarrhea or constipation, abnormal anatomy or neurologic function, inflammatory bowel disease, and allergies including food allergies. If your cat experiences recurrent anal sac disease, he should be assessed and treated for any underlying conditions to reduce recurrence. If your cat has several episodes of anal sac disease and recommended treatments, such as dietary changes and supplements or medications 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.

"Removal of the anal sacs is a delicate and specialized surgery."

Some cats will experience a 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 veterinarian as soon as any clinical signs are seen.

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