Perianal Fistulas

Also Known As: Anal Furunculosis

Transmission or Cause: Perianal fistulas are caused by inflammation of the tissues around the anus causing extensive swelling and ulceration. The cause is not clear but dogs with perianal fistulas are suspected to have immune dysfunction. Some people believe that colitis and perianal fistulas in the German Shepherd Dog is similar to Crohn’s Disease in people.

Affected animals: The majority of cases of perinal fistulas occur in German Shepherds. Irish Setter are the second most common breed but some other breeds reported include Labrador Retrievers, Old English Sheepdogs, Border Collies, Bulldogs, and some mix breeds. Middle aged intact male dogs are most often affected.

Clinical signs: Common clinical signs include: difficult and painful defecation, perianal licking and chewing, foul smelling perianal discharge, low tail carriage, weight loss and lethargy. Some dogs may have concurrent inflammatory bowl disease. The lesions can develop gradually and signs may not be noticed by the owners for a long time.

Diagnosis: Diagnosis of perianal fistulas is based on history, clinical signs and by ruling out other causes of perianal inflammation. A rectal exam is usually performed and since perianal fistulas are very painful, the dog may have to be sedated to examine the area thoroughly.

Prognosis: The prognosis is variable. Many dogs need lifelong control with anti-inflammatory medications and some may undergo temporary remission.

Treatment: Treatment of perianal fistulas may involve antibiotics for secondary infections, long term (3-5 months) anti-inflammatory therapy with cyclosporin or oral steroids, topical anti-inflammatory ointment such as tacrolimus and diet manipulation. Surgery following medical therapy to remove residual lesions may be helpful in some cases.

Prevention: There are no known preventative measures to avoid the development of perianal fistulas.