ANAL FURUNCULOSIS (1)
by Trevor Turner  BVetMed, MRCVS, FRSH, MCIAb, MAE

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Anal furunculosis or perianal fistula as it is called in North America is a subject about which many German Shepherd Dog owners have very real concerns. This is the impression that I gained when I have talked with many GSD owners out of the veterinary environment at shows, trials etc. Although by far the greatest preponderance of cases occur in GSDs and GSD crosses, I have seen occasional cases in Collies, Sheepdogs and Labrador Retrievers.   During the years of my particular involvement with the condition and its treatment I also received a fair number of the larger terriers and Schnauzers with  `look-alike’ signs of anal furunculosis with obvious perianal sinuses. These, on investigation, invariably  turned out to be proctitis and perianal pyoderma rather than true anal furunculosis. Recent studies have shown that the  Leonberger also suffers from the syndrome.

I became interested in the condition nearly 30 years ago when I developed an interest in cryosurgery and certainly for the ensuing 20 years felt that a cryosurgical approach to the problem, in my hands, resulted in the best chance of success.     Some patients responded dramatically and after one session of cryotherapy under a general anaesthetic, needed no further treatment.  These however were the exception, the majority needed repeat treatments and in some, alas, we never got on top of the condition.

Over the years, after treating many hundreds of cases I began to doubt whether the `rotting anus’ was indeed the main problem for these poor dogs. It seemed to me that an increasing proportion suffered other chronic conditions including chronic dermatitis and probably most commonly, bowel upsets.  These varied from mild gastritis, `bilious attacks` to chronic diarrhoea.   These dogs were often found to have inflammatory bowel disease, (IBD), due to food allergies or some immune mediated problem.

Pannus, a particularly GSD prone condition of the eye, leading eventually to pigmentation of the cornea, was also often noted.

Gradually it was being recognised by the profession that pannus and IBD were primarily immune mediated conditions.  I began to think along the same lines in respect of anal furunculosis.   This was  long before a formal research project was set up at Bristol Vet School.  Perhaps it was a bit “putting the cart before the horse” but I tried to address the common bowel conditions in these dogs presented with sore backsides, solely from the simplistic view that any surgery I performed at the rear end would have a better chance of success if the dog was not continuously washing it in uncontrolled faecal voiding.

Year on year the rear end of the GSD has provided endless topics for discussions at BSAVA. If it isn’t hip dysplasia, then it is anal furunculosis with an endless variety of speakers from home and abroad, me included.

A couple of years ago I was fascinated to listen to Dr Dick White from the Queens Veterinary School Hospital, Cambridge, discussing whether the condition was surgical or medical. Despite being a surgeon he was unequivocal that the condition should now be treated as a medical rather than a surgical problem.  This was basically due to the fact that recent work had shown that the condition did appear to be immune mediated.  It has many similarities with human Crohne’s Disease.

Recent work has indicated that the disease really represents only one aspect of abnormal immune function.  This has resulted in a tremendous change in the management of the condition.  Further investigation also confirmed that anal furunculosis is frequently accompanied with IBD.

The advent of commercially available hypo-allergenic diets led to a major break through in the control of diarrhoea and gas formation in with chronic bowel disease.   If these dogs also suffered anal fistulae, it was noted they showed improvement around the anal region following treatment that stabilised if not cured the bowel problem.   It was for these reasons that over  the last several years there has been this gradual  shift towards medical rather than surgical treatment for anal furunculosis.

Treatment today is directed towards dietary management and the control of the immune problem as a whole rather than simply treating the perianal fistulae.  Over the years these have been subject to a tremendous variety of treatments, the proponents of which all claim success, me included with my cryosurgery!  Treatments have varied from tail amputation to cauterisation of the fistulae through meticulous surgery to cryosurgery and laser therapy. 

It is a sure sign that we do not know the cause and therefore cannot design a logical treatment when  such variety of `cures’ is on offer.

Years ago in the really refractive cases I would use corticosteroids (cortisone) , solely to reduce the inflammation and make the dog more comfortable.  Today the same drug is frequently used in high immunosuppressive doses initially.  This is then reduced and continued long term at the reduced dose.  This is often combined with newer immunosuppressive drugs such as Cyclosporine.  In  really refractive cases this combined with hypo-allergenic diets has resulted in spectacular improvements in up to 90% of cases treated.

Cyclosporine is the immunosuppressive drug of choice and sometimes its effect is little short of miraculous.   However the one drawback is its price. Using cyclosporine on a dog the size of a GSD will soon exhaust  insurance cover!

What was I saying about the ever green nature of the subject at BSAVA? This year I listened to Bryden Stanley from Michigan State University, speaking on the subject.  She made it quite clear that local cleansing of the affected area with topical and systemic antibiotic medications was palliative at best and historically they always ended up at the surgeon’s door!  Her view was that surgery yielded satisfactory short term results in up to 80% of cases but recurrence rates were high, (50-90%)  and complications not uncommon.  Using cryotherapy I would not put recurrence rates at more than about 30% but they certainly did occur, the most common of which were faecal incontinence and anal stricture.  However both of these conditions could be controlled in the majority of cases. 

Dr Stanley then discussed the results of using cyclosporine combined with ketaconozole.

This allows a much lower dose of cyclosporine to be used  thus reducing the cost, although of course the ketaconozole then has to be paid for.  This is much more reasonable than the cost of cyclosporine so the treatment becomes almost affordable.

Combine the treatment with corticosteroid therapy and a suitable diet, usually involving an alternative protein source and a high success is achievable long term.

The question then remains, what about the anal sacs? (glands)  In retrospect one of the reasons for my continued belief in cryotherapy was perhaps the fact that I always ensured that the anal glands were surgically removed before cryosurgery was attempted.  This was solely because the majority of anal sacs that I examined in dogs presented with anal furunculosis were invariably chronically infected.  It was my belief that leaving  these in place resulted in a continual source of re-infection.  Perhaps I was naïve but during her presentation I felt Bryden Stanley emphasised the need for anal sac removal.

I would be interested to learn from any readers whose dogs have been treated with cyclosporine.