Recurrent anal sac trouble: why it keeps happening and how to break the cycle

Here is the single most important idea to carry through. Recurrence is usually a sign of an underlying driver that repeated emptying does not fix, not a fault in the sacs themselves. The full sac is the downstream sign; something upstream keeps pushing it that way, and until that is found and managed, you can empty the sacs forever and the cycle simply resets.

And it is a real cycle, not an unlucky run. Anal sac disease is common, with a one-year prevalence of 4.40% in the largest UK primary-care study of 104,212 dogs (O'Neill et al., 2021). Most dogs have a single episode and never look back, with 126 of 190 dogs (66.3%) in one referral series of anal sacculitis having only one (Hvitman-Graflund et al., 2023). But that leaves roughly a third who recur, and those dogs are the readers of this article. If your dog is on a repeat schedule, you are not imagining the pattern.

The drivers are not equal, and the evidence behind them is not equal either, so let me take each honestly.

Allergic skin disease is the big one. In that 190-dog study, cutaneous allergic disease (atopic dermatitis, whether environmentally or food-driven) was the most common concurrent condition, occurring significantly more often than in the general practice population, and dogs with concurrent allergic skin disease were significantly more likely to recur than those with other comorbidities (Hvitman-Graflund et al., 2023). A separate referral series found atopic dermatitis the commonest comorbidity, in 12 of 33 dogs (Lundberg et al., 2022). The proposed mechanism: inflammation and self-trauma around the back end narrow and swell the tiny duct that drains each sac (a duct stenosis), so the sac cannot empty normally, and impaction and infection follow (Lundberg et al., 2022).

I want to be straight about the limits. These are retrospective associations: allergy and recurrent anal sac trouble clearly travel together, but the studies cannot yet prove that treating the allergy fixes the sac problem, and the 190-dog study says so itself, that further work is needed to know whether managing the skin disease reduces the risk (Hvitman-Graflund et al., 2023). So I will not promise you a cure. What I will say plainly is that in a dog who keeps recurring, investigating and controlling an underlying allergy is the most logical and best-supported thing to chase. The skin side of that work-up, the itchy dog and the food-reaction detail, belongs to the Allergies and Skin space, set out in food allergies explained.

Persistently soft stool is a plausible driver for some dogs, but the evidence is older and inconsistent. The classic teaching is that a firm stool presses on the sacs and empties them as it passes, while chronically loose stool does not. That traces back to Halnan, who found over half of affected dogs were on all-meat, biscuit-free diets producing a thin, strap-like faeces that did not empty the sacs (Halnan, 1976). But modern series have not consistently reproduced it: a later study found poor stool quality in only about a fifth of dogs, so the fair verdict is that stool quality may matter for some individuals but is not a universal cause (Today's Veterinary Practice review, 2025). Treat it as one real driver worth checking, not the explanation for every case. How to judge and report stool quality is owned by describing symptoms to your vet, and the Faecal Score Tracker is how you and your vet watch whether a change is landing.

Body condition probably matters less than folklore says. Despite the common claim that fat dogs get anal sac trouble, the large UK study found no association between obesity and anal sac disease at all (O'Neill et al., 2021), and referral series show mixed body condition, so obesity's role may be smaller than long assumed (Today's Veterinary Practice review, 2025). Keeping your dog lean is worth doing for a dozen good reasons, but I will not sell it as the proven cause of recurrence.

Some dogs are simply built for it, and that is nobody's fault. Six breeds had significantly raised odds in the UK study, led by the Cavalier King Charles Spaniel and the King Charles Spaniel (each over three times the odds of a crossbred), then the Cockapoo, Shih-tzu, Bichon Frise and Cocker Spaniel, while several larger breeds such as the Labrador had reduced odds (O'Neill et al., 2021). If you own a predisposed breed, the constitution is part of the story, which shifts the emphasis from blame towards steady management.

Expressing a sac empties it, and when a sac is genuinely full and uncomfortable that is the right thing to do. But it does nothing about why the sac keeps filling abnormally. Repeated expression treats the symptom; it is not a cure for recurrence, and routinely emptying a comfortable, clinically normal sac on a calendar is not an evidence-based way to prevent the problem returning. You will sometimes read that frequent emptying "creates a dependency" or scars the duct; that idea is widely repeated, but I could not find solid primary evidence for the mechanism, so I will not state it as fact. The message stands without it: do not lean on repeated emptying as a fix, and put the effort into finding the driver.

Where an allergy is the suspected driver, the logical next step is a properly run food elimination trial using a limited-ingredient or hydrolysed diet, and recurrent anal sac trouble alone can be reason enough to consider one (Clinician's Brief, 2023). The cutaneous side belongs to Allergies and Skin, but the Diet-Trial Companion is the natural tool to run and track it, so the weeks of effort produce a clear answer.

For the infected, inflamed sac there is also a useful middle step between repeated expression and surgery: flushing the sac and infusing a combined steroid, antibiotic and antifungal preparation directly into it, which achieved remission in most of a series of 33 dogs (Lundberg et al., 2022). Like expression, though, it treats the episode rather than the cause, so it can need repeating if the driver is left unaddressed. (The wider question of oral antibiotics for the gut is owned by antibiotics for diarrhoea.)

For the dog whose problem genuinely will not settle, surgery to remove the sacs (anal sacculectomy) becomes a real option. It is reserved for disease that is recurrent, chronic or persistent despite appropriate medical management, ideally after a proper attempt to find and treat the driver, not as an early step, because most cases respond to local treatment and to controlling the contributing factors first (Davis & Hosgood, 2025).

The procedure has a frightening reputation, mostly because owners hear one word: incontinence. The fear comes from older surgery, where a classic series of 95 dogs recorded long-term complications including faecal incontinence, fistulation and stricture in a subset (Hill & Smeak, 2002), and the risk is genuine because the nerves controlling the back passage run close to the sacs. I will not pretend that away, but the contemporary picture is much kinder. In 50 dogs done by a modified closed technique, 42% had a complication, yet the great majority were minor and had resolved by the two-week recheck, with no permanent incontinence documented (Davis & Hosgood, 2025). In 62 dogs done by a closed technique, about a third had complications, all mild and self-limiting, and none developed permanent faecal incontinence (Charlesworth, 2014). A newer inside-out technique in 28 small dogs and cats had a complication in only one, a mild incontinence resolving within a week, against historical rates of around 17 to 32% (Lee et al., 2023).

The fair summary is this: temporary changes in the early weeks, some soiling or weak tone as the area heals, are not unusual, but lasting incontinence is uncommon in modern series. Two nuances help the decision. Smaller dogs (under 15 kg) were more likely to have postoperative complications, while a previous abscess or recurrent disease did not worsen the outcome (Charlesworth, 2014), so a history of abscesses is not a reason to expect a bumpier operation. And if only one sac is the troublemaker, removing just that one is possible, which further limits the risk. One last thing: if your dog is older, or the sac feels persistently abnormal or has a lump, ask your vet to exclude other causes first, because not every chronically abnormal sac is simply a stubborn one.

If you take one thing from this, let it be that most recurrent cases can be brought under control, but by a plan rather than a string of disconnected visits. That plan has three honest parts. First, find and treat the underlying driver: an allergy work-up where the signs point that way, attention to poor stool quality, and a sensible eye on body condition. Second, treat flares in a targeted way, emptying the sac when it is genuinely full and using local intra-sac treatment for sacculitis, rather than reflexively emptying comfortable sacs on a schedule. Third, keep surgery in reserve for the genuinely refractory or chronically infected sac, eyes open to the small, mostly temporary continence risk and the high chance of a cure.

What turns that from theory into something you can see working is tracking. Logging stool quality with the Faecal Score Tracker and noting how often episodes happen is the difference between firefighting and managed care: you stop guessing whether the new diet or the allergy treatment is helping and watch the gaps between flares stretch out. And if a flare ever turns into the acutely painful, rapidly swelling abscess that needs same-day attention, digestive emergencies sets the threshold.

The cycle you are stuck in is real, but it is not unbreakable. It just needs someone to stop emptying the same sac and start asking why it keeps filling.

Charlesworth, T. M. (2014). Risk factors for postoperative complications following bilateral closed anal sacculectomy in the dog. Journal of Small Animal Practice, 55(7), 350-354. https://doi.org/10.1111/jsap.12200

Clinician's Brief. (2023). Recurrent anal sacculitis and facial pruritus. Clinician's Brief, May/June 2023. https://www.cliniciansbrief.com/article/anal-sac-abscess-dog-suspected-adverse-food-reaction

Davis, A. T., & Hosgood, G. L. (2025). Modified closed sacculectomy in 50 dogs with non-neoplastic anal sac disease. Veterinary Surgery, 54(2), 382-388. https://doi.org/10.1111/vsu.14168

Halnan, C. R. E. (1976). The frequency of occurrence of anal sacculitis in the dog. Journal of Small Animal Practice, 17(8), 537-541.

Hill, L. N., & Smeak, D. D. (2002). Open versus closed bilateral anal sacculectomy for treatment of non-neoplastic anal sac disease in dogs: 95 cases (1969-1994). Journal of the American Veterinary Medical Association, 221(5), 662-665. https://doi.org/10.2460/javma.2002.221.662

Hvitman-Graflund, K., Sparks, T., & Varjonen, K. (2023). A retrospective study of treatment, outcome, recurrence and concurrent diseases in 190 dogs with anal sacculitis. Veterinary Dermatology, 34(6), 576-585. https://doi.org/10.1111/vde.13205

Lee, S. G., Jeong, S. M., Bae, S., Park, Y., Moon, C., & Kim, H. Y. (2023). Inside-out anal sacculectomy in small dog breeds and cats. Frontiers in Veterinary Science, 10, 1105826. https://doi.org/10.3389/fvets.2023.1105826

Lundberg, A., Koch, S. N., Torres, S. M. F., & Furrow, E. (2022). Local treatment for canine anal sacculitis: a retrospective study of 33 dogs. Veterinary Dermatology, 33(5), 426-434. https://doi.org/10.1111/vde.13102

O'Neill, D. G., Hendricks, A., Phillips, J. A., Brodbelt, D. C., Church, D. B., & Loeffler, A. (2021). Non-neoplastic anal sac disorders in UK dogs: epidemiology and management aspects of a research-neglected syndrome. Veterinary Record, 188(2), e203. https://doi.org/10.1002/vetr.203

Today's Veterinary Practice. (2025). Canine anal sacculitis: a brief review with a focus on the recent literature. Today's Veterinary Practice, Sep/Oct 2025. https://todaysveterinarypractice.com/dermatology/canine-anal-sacculitis/