Getting to the bottom of anal sac diseases

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Anal sac diseases, including anal sacculitis, anal sac impactions, anal sac abscesses can all cause discomfort when sitting or defecating. These diseases may cause the patient to scoot, lick, or bite the anus area. Although anal sac diseases are not the most glamorous condition of veterinary medicine, Julia E. Miller, DVM, DACVD, a dermatologist with Animal Dermatology Group in Louisville, Kentucky, and an assistant clinical professor of dermatology at Cornell University College of Veterinary Medicine in Ithaca, New York, argues that it is important to not shy away from them.

During her session sponsored by VetBiotek at the Fetch dvm360 conference in Nashville, Tennessee,¹ Miller told attendees, “What I want to remind you of is dogs and cats will often let us know that there's a problem going on, right? So, this dog is chewing its tail; what's another really good differential for this? Yeah, fleas. And should you always rule out fleas first? Yes. If you rule out ectoparasites in any itchy dog, you're the greatest person and you're halfway to being a dermatologist. So, ruling out ectoparasites in all itchy creatures at all times is critical.”

The precise cause of anal sac impactions is unknown, but several potential mechanisms have been suggested, including soft stools, obesity, poor muscle tone, and damage to the ducts from frequent manual expression.^1,3 Recurrent or chronic anal sac disease may also be linked to underlying allergies (either food or environmental), making it essential to diagnose and address these conditions for effective management.

Diagnosis

For physical identification of anal sacs, Miller said, “This is my clock face analogy. And anal glands/anal sacs live between 4 and 6, and between 6 and 8 [on a clock]… So whenever I am looking at the back end of an animal, I want to know where it sits on the clock face because that can help me decide if this is a perianal fistulas or is this an anal sacculitis issue.”

Although diagnosis can be made by physical examination, Miller also recommended doing cytology when anal sacculitis is suspected and the anal sac is palpably thickened or blood is found on expression. Miller stated, “What is not normal is blood. Every single time blood is not normal.”

She stated that in normal anal sac cytology you may see a mixed bacterial population, a very small number of yeast, and/or a very small number of white blood cells. It is abnormal to see red blood cells, a moderate to large number of white blood cells, white blood cells with intracellular bacteria, or a moderate to large number of yeast.^1-3

“I can absolutely diagnose anal gland infections with cytology, just like you would do a skin infection. If you're wondering how to do it, I will express the anal glands and, inevitably, it gets on my glove, and I literally just tap it on the slide and I do a squash smear. I do anal sac cytology all the time,” Miller told attendees.

When collecting a sample for culture, ensure that the perianal area is thoroughly cleaned and include the anal sac. This will help prevent the culture results from being unclear or crowded with contamination.

Management

First flush the anal sac to thoroughly clean it. According to Miller, managing anal sacculitis that has not progressed to abscessation can be accomplished with focal, topical treatment. “I am a huge fan of topical therapy, a huge fan of it. When the anal gland has not ruptured yet, I think this works incredibly well for the vast majority of these [cases],” she said.

If the anal sac is already ruptured, Miller advised prescribing an oral antibiotic and use pain management strategies with a warm compress to help the patient slowly heal on its own. The bacteria typically seen with these types of infections are proteus, E coli, and enterococcus. “And how long should you do it for? That's the million-dollar question. I think 7 days can be enough in some of them. But I'm a big 3-week person because that's how I treat skin disease. I would rather treat too long than too short. That is my antibiotic rule,” Miller explained. “I'd rather overdo it than under do it. Because once I'm going the route of an oral antibiotic, people will say ‘well, is that good and antimicrobial stewardship?’ Let me tell you what bad antimicrobial stewardship is, [it's] choosing the right antibiotic and doing it for too short a period of time. That is the exact way you create resistance. Because what have you done, you've killed 90% of the bacteria you've left 10, and they get nasty resistance.”

Infusion would be effective for chronic anal sac diseases and reduce the inflammation caused by these conditions. Miller also explained Phovia a product by Vetoquinol: “What Phovia is, is it's fluorescent light therapy that helps heat [and] essentially heal deep tissue wounds and superficial wounds as well. [It also has] great antimicrobial stewardship.”

References

1. Miller JE. No Butts About It: Anal Sacs, Tail Glands, And Fistulas Oh My! Presented at: Fetch dvm360 conference; Nashville, TN. May 17, 2024.
2. Lake AM, Scott DW, Miller WH et al. Gross and cytological characteristics of normal canine anal‐sac secretions. J Vet Med. 2004; 51: 249‐253
3. Paterson S, Steen S. Anal sacs: a new approach to an old problem? Vet Prac. 2016: 31‐33.