Surprise — Cats Have Anal Sacs, Too

Does your cat sometimes leave a “fishy” smell on your lap?

Well, it might be that the anal glands (anal sacs) are overfull and your cat anointed your lap with that disagreeable scent. Lucky you.

The smell is somewhere between overripe cheese and rancid fish. In other words, not pleasant.

Different From Dogs

With regard to anal glands: Newsflash! Cats are different from dogs…and yet somewhat the same. Many people are surprised that cats have anal sacs, and this reduced awareness is probably because cats have fewer anal gland problems.

Also, whereas our canine companions are obsessed with butt-sniffing and sampling scent signatures, our feline friends are more refined. Nose-touching and visual displays are a cat’s primary means of greeting, with “anal awareness” in third place.

Territory Marking

Cats use their anal sac secretions to identify their territory. Small amounts of secretion are squeezed onto each bowel movement and are the equivalent of a poster advertising that “Fluffy lives here.”

If you want the full lowdown on what makes up anal sac secretions, here goes. They are a mix of volatile carboxylic acids such as:

• Acetic acid
• Butyric acid
• Isocaproic acid
• Priopinic acid
• Valeric acid

Cat Anal Sacs

Anal sacs sit like 2 small grapes sandwiched between the 2 muscular rings of the anus, at the 20-past-8 position on a clock face.

The sacs are lined by glands that produce a strong-smelling, oily secretion. When the cat goes to the toilet, contractions of the anal ring squeeze the secretion along 2 tiny ducts and onto the stool.

Problems are not as common in the cat as in the dog, which may be partly because cat secretions are thinner and easier to express, leading to the sacs emptying more completely. But this doesn’t mean cats never have problems.

Anal Sac Disease

If one factor changes, then emptying the anal sacs may get thrown off balance.

For example, if the cat has an upset tummy, the glands aren’t squeezed so much. Or if the cat produces a thicker secretion, it becomes harder to expel. Either could lead to a secretion buildup within the glands.

Cats are generally quite stoic when it comes to their anal glands, and problems are often advanced before they show signs, including:

• Scooting: Rubbing their bottoms along the ground
• Biting: Biting at the fur around their anus (look for patches of barbered hair)
• Licking: Obsessive licking around their bottom
• Crying: Signs of discomfort when passing a bowel movement
• Swelling: Puffiness around the anal area
• Discharge: Foul-smelling discharge from the anal area
• Smell: An unpleasant smell that follows the cat around or is left where the cat sat

Anal Sac Problems

The most common problem is impaction caused by blockage of the draining duct. The sacs continue to produce secretion, so the pressure builds within the gland, causing discomfort.

Left untreated, bacteria in the impacted material can fester, and infection results. This is even more uncomfortable, and sometimes the glands will rupture (thankfully, anal sac cancer is extremely rare in cats).

Expressing Anal Sacs

Although it might be tempting (if that’s the right word!) to try emptying the sacs at home, leave it to the professionals. For starters, cats don’t like having their glands expressed, especially when they’re sore, so minimizing the discomfort by letting your veterinarian do the procedure is fairer all around.

Secondly, not all licking/scooting/bad smells are caused by anal glands. The cat may have an abscess, an allergy or a parasitic infection. Therefore, it’s important to confirm the diagnosis so that the problem is treated correctly.

In addition, underlying factors must be addressed. For example, if your cat has an upset tummy, then it’s important to get to the bottom of that, or the anal sac problem will keep recurring.

To Express or Not to Express?

If your cat has had anal gland problems in the past, the vet may recommend expressing the glands every 3–6 months. However, there is some controversy over whether it’s right to express healthy anal glands.

The argument against it is that manually emptying the glands can make them “lazy” — they may not work so effectively afterward, and the cat becomes reliant on manual intervention. However, the counterargument is that occasional emptying is so infrequent that it shouldn’t cause problems.

This seems sensible, and it could also catch glands that are newly impacted and prevent the distress of infection, so this sounds like a good compromise if your cat suffers from irritation around the back end.

This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 13, 2018.