Anal Furunculosis

Audra Lynn

What is Ana Furcinculosis? 

Anal Furcinculosis (perianal fistulas) are deep unsightly sinuses that track through the skin, sometimes with flat open areas of ulceration.  This can be a debilitating disease.  These ulceration are usually confined to the skin around the anus, but in severe cases they can spread down the hindlegs and to the flanks.  Technically they are NOT fistulas because they course only within the skin and do not open into another organ.  Even though they are near the anal sacs the sinuses do not connect with them, nor do they connect with the rectum or colon.


What Causes them? 

The cause is unknown.   The sinuses are not caused by infection, although secondary bacterial infections can occur.  Some believe that dogs that carry their tails tightly against the anal region Kay be predisposed to develop furunculosis due to poor ventilation, but nothing has been proven.  Others have suggested that there may be impaction of the local crypts of Morgagni. When the sinuses are tacked back to their source they do not reach the anal sacs or the rectum or colon, as was suggested by some authors who were comparing the disorder with Chrohne's disease in humans. 

What Breed does this occur in?

It is almost exclusive to the German Shepherd Dog. It usually is seen initially in both sexes ages 3-8 years old. 

What signs do I need to watch for?

These skin lesions are irritable resulting in self-trauma, and affected dogs often lick and bite at the affected region.  They may have pain, difficulty, reluctance, or straining during defaecation.  If these 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.  

What complications can they cause?

Once a dog gets them 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.  

How to diagnose?

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

How can I treat them?

Unfortunatley drugs alone generally does not successfully treat them, except for using cyclosporin.  They have been running studies and 6 cases have been successfully treated of anal furunculosis with the drug cyclosporin, at a dose rate if 7.5 mg twice a day.  Cyclosporin is a drug that suppresses the immune system.  Signs of the disease disappeared within a week, the size of the skin lesion decreased by 50-90% and the skin stayed healed during 10-20 weeks of treatment.  One case required cryosurgery to get healing of a small area of skin, and one case suffered a relapse 8 weeks after treatment was stopped.  The number of dogs in this study was low at 6, but nevertheless this does offer an alternative method of treatment. 

There are also two other reports of the use of cuclosporin in combination with antibiotics to successfully treat furunculosis, but they reported recurrence if the disease in 10 out of 27 dogs that were treated.  

What is the prognosis?

The prognosis is guarded as recurrence is common

What Life long problems can this cause? 

It can cause faecal incontinence of the anal sphincter control is lost.  


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