ANAL FURUNCULOSIS (Perianal fistulas)

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This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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Anal furunculosis (or perianal fistulas) are deep unsightly sinuses that track through the skin, sometimes with flat open areas of ulceration. They are usually confined to the skin around the anus, but in severe cases they can spread as far as the flanks and run down the inside of the hindlegs. Technically they are NOT fistulas because they course only within the skin and do not open into another organ. Although they are near the anal sacs (scent glands) the sinuses do not connect with them, nor do they connect with the rectum or colon.

Typical furunculosis lesions around the anus of a German Shepherd Dog

The cause of anal furunculosis is unknown. 

The sinuses are not caused by infection, although secondary bacterial infection may be present. Some authors have suggested that dogs that carry the tail tightly against the anal region may be predisposed to develop furunculosis due to poor ventilation but this has not been proved. Others have suggested that there may be impaction of the local crypts of Morgagni. 

When the sinuses are tracked back to their source they do not reach the anal sacs (scent glands) or the rectum or colon, as was suggested by some authors who were comparing the disorder with Crohne's Disease in humans..

Breed Occurrence
The disease occurs almost exclusively in the German Shepherd Dog. It is seen in both sexes and in German Shepherd crosses as well. It usually initially occurs in dogs aged 3-8 years.


The skin lesions are irritable resulting in self-trauma, and affected dogs often  lick and bite at the affected region. There may be pain, difficulty (or reluctance) and straining during defaecation. If the lesions spread down the legs the dog may walk with a straddled gait. Affected dogs are often tail-shy and won't allow people near their rear end, or to touch or lift their tail.

Repeated recurrences are common, and repeated surgery or cryosurgery can lead to fibrosis making defaecation difficult. Affected patients are often very tail-shy and reluctant to allow inspection of the area , or touching/lifting of the tail

The diagnosis is confirmed at physical examination and by ruling out other causes for the lesions


Treatment with drugs alone has generally not been successful except for cyclosporinmay be efficacious CLICK HERE for more information.

If therapeutic treatment does not work there are two main forms of surgical treatment :

Because of the extent of the lesions these treatments often have to be repeated several times.

The prognosis is guarded as recurrence is common

Long term problems
Faecal incontinence of the anal sphincter control is lost


Updated October 2013