What is it?
Anal furunculosis (AF) is a long term (chronic) painful, debilitating disease of the area around the anus, including the perianal, anal and occasionally the rectal tissue.
What dogs are affected?
The main dog breed impacted by this is the German Shepherd who are highly predisposed; one report suggested that 84% of all cases are seen in the German shepherd.
Many of the German shepherd dogs with anal furunculosis have also been shown to have concurrent colitis, inflammation of the inner lining of the colon (large intestine), suggesting that an immune-mediated mechanism may be involved. In a way it may share similarities with Crohn’s disease in humans; both diseases respond well to suppression/ down regulation of the immune response.
As well as the GSD, a range of different breeds can be affected, including:
- Irish setters
- Collies
- Old English sheepdogs
- Labradors
- Bulldogs
- Spaniels
What are the signs?
The signs of anal furunculosis in dogs can be quite subtle and it is not always obvious initially.
Some of the common clinical signs associated include:
The lesions on the perianal area itself vary considerably in severity, size and shape. Furthermore, as mentioned before, the dogs where the disease may be down to an immune mediated issue may also show gastrointestinal signs.
Gastrointestinal signs include:
How is it diagnosed?
The diagnosis of anal furunculosis can be made by considering the patient’s history, clinical exam, if they are a predisposed breed, and their typical clinical signs.
They may need to be examined under general anaesthetic
AF is a painful condition and to get the whole picture your veterinary team may need to examine the perianal area. This assessment could include assessment of the anal glands and exploration of any tracts; this can only be undertaken successfully in an anaesthetised animal, and will help keep your pet comfortable while they examine them thoroughly.
Samples may be required
Your veterinary team may look at a superficial cytology sample, looking at the cells and any bacteria found on the area, however samples for culture taken from the surface of the skin can give misleading results so your vets may suggest cultures using material gathered by a sterile swab from the sinus tracts (a small abnormal channel) or by tissue culture.
They may need to investigate the gastrointestinal issues too
If your pet also appears to have concurrent gastrointestinal signs your vets may suggest a hypoallergenic diet and if your pet has very severe gastrointestinal signs a colonoscopy with biopsy may be useful too.
What is the treatment?
The management of AF will depend on how bad the anal lesions are and also the temperament of the dog!
Medical treatment
Sadly, many dogs with AF are so painful they will not tolerate topical (applied directly to the area) medication, especially initially, which can be useful in many of the milder cases. Your vet will prescribe the best treatment for your pet if it is suitable.
Recent studies looking at medical therapy of AF using immunomodulating and immunosuppressive drugs has led to a good resolution of AF in many cases without the adverse effects seen in surgical cases. Medical therapy is best alongside hygiene measures and dietary changes.
Immunosuppressive and immunomodulatory drugs modify the way the immune system behaves, and are the mainstay of treatment for AF. This may include systemic therapy (tablets or injections) with glucocorticoids with or without azathioprine and/or metronidazole; ciclosporin with or without ketoconazole or itraconazole; azathioprine with metronidazole or sulphasalazine.
Surgical Management
Prior to the use of immunomodulating drugs (drugs that target immune pathways), AF was managed surgically. We now have more options at our disposal, but surgical intervention is sometimes required.
Surgical interventions previously may have included:
However, the rate of resolution of AF after surgery ranges vastly. With some literature suggesting resolution was as high as 97% to as low as 48%. However, the potential side-effects after surgical therapy could also be negative given the area of treatment. Side effects may include anal stenosis and faecal incontinence which when severe can lead to the euthanasia of patients.
It is thought that if surgical therapy is deemed necessary, after weighing up the pros and cons, when it is performed after medical therapy, the success rate is much higher.
As a result, surgery is usually reserved for cases that continue to suffer from lesions despite medical therapy or those with frequent recurrences. Surgery is best undertaken once the lesions around the bottom are small enough to avoid the need for reconstructive skin closure techniques (plastic surgery) - as you see above, a big surgery around the anus can lead to other negative side effects that we want to avoid!
We need to remember that the success rates after surgery does vary, however about 90% of dogs are cured in appropriately managed cases.
Diet change
As said before, many cases have concurrent gastrointestinal issues and some have likened the disease to that of Crohn's in humans. Dietary therapy has been shown to be useful particularly where the dog has a history of colitis.
Diets should be formulated on an individual basis so that a novel protein, a protein source new to the patient, should be fed. However, there have also been diets formulated by companies especially for this kind of issue; these are hydrolysed diets that are available commercially.
Where the dog has signs of dyschezia (difficulty pooing), stool softeners may also help make the dog more comfortable when it goes to the toilet.
Hygiene measures and therapy
There are a number of things we can do to help with hygiene and aid in better healing of the lesions.
Antibiotics should be prescribed on the results that come back from your dog's culture and sensitivity swab together with topical treatment of the area; only if the dog will tolerate it! Keeping the area free from dirt, faeces and hair can help - clipping and cleaning the area is important to prevent faecal matter staying around the area.
Will it get better?
At least 95% of cases will significantly improve following medical therapy, with lesions reducing in size between 60% and 100%.
However, it is important to remember that drug therapy usually lasts from 4-24 weeks with most patients responding within 12 weeks – it will take time to get better and will take lots of dedication and patience from you and your veterinary team.
Will it come back?
Up to 85% of patients go into complete remission (lesions disappear) using medical therapy, however, approximately 40% of these cases can suffer recurrence of the disease, so it is important to factor that in so you can manage your expectations of the disease and the financial implications of treating this.
If recurrence occurs it usually does so within six to eight months after treatment is stopped. Patients suffering from recurrence often respond to additional courses of medical therapy. Sadly, approximately 4% of cases do not significantly improve with medical therapy - however, this means that 96% of dogs will improve, usually dramatically.
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