Anal Sac Disease In Dogs And Cats

Anal sacs are reservoirs for scent material produced by microscopic anal glands. Every dog and cat has two, and they are located at 5 o’clock and 7 o’clock from the center of the anus, inside the external anal sphincter muscle. They are connected to the outside of the body by way of small ducts which open near the anal orifice.

The purpose of this incredibly stinky scent material is to provide a means of marking one’s territory. As domesticated dogs and cats no longer have a need for territory marking, these structures have become vestigial. Like other vestigial organs, such as the appendix, they sometimes don’t work properly. We will discuss normal function as well as complications that can occur from malfunction.

When our pets end their bowel movements, they do so with contraction of the internal and external anal sphincter muscles. Sphincters, by definition, are round, so there is a purse-string action when they contract. For the anal sphincters the contraction applies pressure to the stool and the stool falls to the ground. Normal anal sac material is a paste consistency, and contraction of the external anal sphincter muscle simultaneously applies pressure to the sacs, squirting a small amount of scented paste onto each pile of stool.

If the process works as it is supposed to and there are two to four bowel movements per day, the flow of anal sac material keeps the pathway open and the anal sacs stay a comfortable size.

Several factors can upset the balance and result in problems ranging in severity from uncomfortable to life-threatening.

The most common complication is anal sacs that become overly full. Physical problems that may contribute to this outcome include inactivity, obesity, diarrhea and constipation. Pet foods too low in fiber can be a factor.

When the anal sac material fails to flow regularly, it becomes inspissated. The microscopic anal glands continue to produce scent material and the sacs become more and more full. As pressure inside the sacs increases a pet feels the discomfort and instinctively wants to relieve that pressure. Many pets will drag or “scoot” the perineal region in an effort to apply sufficient pressure to force material out of the sacs. If they are successful, you will see a smudged track of greyish-brown paste that smells a little like dead fish.

Really dead fish.

Resist the urge to check your homeowner’s policy to determine whether it is paid up. Arson is punishable by imprisonment, and you can effectively cancel the odor by a thorough application of rubbing (isopropyl) alcohol. Not all fabrics are color-safe to alcohol, so test an inconspicious area first.

If your pet also smells bad, don some plastic gloves, apply rubbing alcohol to a paper towel and wipe the perineum. Repeat as needed. If required, your pet can be bathed after the smell is diminished.

Pets will sometimes use extremely abrasive surfaces for their scooting, such as carpets and even concrete. If redness and/or bleeding occur you should consult with your pet’s doctor about an ointment or other treatment for the resulting lesion.

Repetitive scooting, licking the perineum, crying in pain and further evidence of lack of success in emptying the sacs means that human intervention will be required. Call your veterinarian for an appointment for him to manually express the anal sacs. Some clinicians may have their groomers or lay staff perform this task if there are no medical complications such as infection or dermatitis. Anal sac expression is usually performed on the awake patient. There may be short-term discomfort, but it is usually mild.

Those patients with a low threshold of pain (like me!) may require sedation.

Please note that we express anal sacs, not anal glands. As mentioned above, anal glands are microscopic, too small to empty individually. Anal glands provide the scent material that fills anal sacs.


The vast majority of pets nationwide never have their anal sacs emptied by a human in their entire lifetimes. These pets simply do it themselves at each bowel movement, as nature intended.

However, if your pet drags his rear or licks his perineum, you should quickly have his anal sacs emptied.

Some other common causes for this same itchy behavior include tapeworms, allergy, stool stuck in the hair and constipation.


Sometimes fecal bacteria will travel up the ducts from the anus to the sacs and begin to multiply inside the anal
sac(s). Usually this is a unilateral problem. Infection results, and most commonly erodes through the wall of the sac, the external anal sphincter muscle and the overlying skin, resulting in a gaping wound that drains pus. Longhaired pets may produce mats that obscure the wound.

Treatment of the lesion requires clipping the surrounding hair, surgical irrigation of the abscess, systemic antibiotics (injectable and oral) and topical administration of ointment to keep the wound open, allowing it to heal from the inside.

Amazingly, anal sacs heal, rebuild their structure and resume their function. The sac on the opposite side will commonly become involved in a separate incident.

Above I’ve described the best scenario in with anal sac abscessation. In a bleaker picture, infection can travel inside instead of outside, resulting in a pelvic abscess. Access to treatment of infection and structural problems in the pelvis is very limited, and pelvic abscesses are frequently fatal. For this and many other reasons, anal sacs which cause dogs and cats recurrent problems should be surgically removed.


The ultimate treatment of anal sacculitis, inflammation with or without infection, is surgical removal. Some surgeons love this procedure. Others hate it.

I think it’s fabulous.

We recommend surgical removal of anal sacs when itchiness and discomfort occur at least once every two months, or when anal sacs have abscessed. Recurrence of infection is not uncommon and avoiding a pelvic abscess can be lifesaving.

The procedure is also indicated when cancer of the anal sac occurs, most commonly in male dogs who have not been neutered.

The surgery involves incising the skin over each sac, carefully dissecting through the external anal sphincter muscle, followed by delicate removal of the wall and duct of the anal sac. If any bleeding occurs it is controlled and the site is closed with sutures. No bandages are required. Activity restriction for about two weeks is routine, as with any surgical procedure.

Some patients will experience temporary fecal incontinence. In my experience most incontinence is resolved in two to three days. Smaller dogs seem to have less tendency to postoperative incontinence than large dogs and, while I’m sure it has happened, I’ve never seen incontinence last more than three weeks.

Anal sacs cause mild to severe problems in pets. Your pet’s doctor is equipped to handle whatever the anal sacs can dish out, including the odor.

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  1. Thanks for the informative article on dogs’ anal sac issues. You mentioned that incontinence can be a side effect of anal sac removal, but typically not for a long time or permanently. I wanted to share with you please about my dog Lexi who had her anal sacs removed 12 months ago (the second sac approximately 6 weeks after the first). Lexi was about 8 years old at the time. She is a very small Rat Terrier who had had 3 litters before we got her from a shelter when she was around 3 or 4 years old. The shelter had Lexi spayed before letting her be adopted. Lexi had had several (10?) bouts of anal sac abscesses over the years, and our veterinarian finally convinced me to have Lexi’s anal sacs surgically removed. After Lexi’s first sac was removed, we were very happy because there were no apparent problems. But since the second, Lexi has been chronically constipated. Only Miralax (PEG), which we discovered about 8 months ago, has been able to cure her constipation. However, if she misses a dose or two, she will still be constipated even today, a year later.
    Also – she has had some strange illnesses in the past year after the surgeries: an unexplained limp (X-rays showed no arthritis, no other test or exam showed anything certain) that has vanished from her front left leg, very hard and swollen mammary glands, bloody stool from once a month to once every six weeks, blood oozing from her anus, a chafed anus, and tooth and mouth pain. She had already had bad teeth before her anal sac removal, and so she had dentistry done about 7 months ago, including several tooth extractions, and a dose of Convenia. Lexi’s doctor finally gave her a second dose of Convenia about 2 to 3 weeks after the dentistry, because that’s when the mammary glands got infected. After this second dose of Convenia, Lexi got ALL better. For about 5 months. Now all of a sudden she has an abscess in her mouth and bloody stool and blood from her anus again. She got a shot of Convenia yesterday for the abscess, to see if it is from an isolated injury or a tooth abscess. But she still has a bloody anus and won’t eat. If you had a moment to think this over and respond, please, I’d be very grateful. Thanks for reading this, and even more if you have any thoughts (please)!-Tom S

    • Temporary incontinence is a common problem after anal sac removal because of the invasion of the external anal sphincter muscle, but I’ve never seen constipation occur post-operatively. I can only assume that the subsequent problems are coincidental, despite the temporal connection. The collection of colitis, oral cavity disease, mastitis and limping doesn’t sound like it could have a relationship, but reminds me of some of the odd diseases women used to experience when they had rupture of silicon breast implants (before saline implants came along). I suppose reaction to any foriegn material in the body could cause a similar reaction. Possibly an autoimmune condition [ ] of some type could be in play, as could septicemia, a circulating, systemic bacterial infection. If limping were a repeated problem I would want to test for tick-borne diseases such as Erlichiosis, Anaplasma, RMSF and Lyme Disease. Meanwhile, you could check to see whether her platelet count is down, an inexpensive but non-specific screening test. At the next episode you could request blood cultures, although they are notorious for false negative growth and can be pricey. I hope this helps, and I hope you will keep us posted on Lexi’s status. Best wishes, Dr. Randolph

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