This is a disease seen most often in middle age intact male German Shepherd dogs but is not exclusive to the breed. It is characterized by progressive deep ulcerated tracts in the skin and tissues surrounding the anus. The cause of the disease is not completely understood but is likely related to a number of factors. These include infection of the skin and glands around the anus, the broad based tail which is carried low covering the anal skin and preventing air circulation, and recent evidence suggests an immune system component such as food allergy or a form of inflammatory bowel disease is also likely involved.

Historical indications include anal discomfort, constipation, diarrhea, foul odor, excessive licking of the area, scooting, straining to defecate and pain induced aggression when the tail is manipulated or the hindquarter is touched. Lesions usually begin as small punctate tracts that may be hard to visualize initially. As the disease progresses, the tracts increase in size and more swelling and ulcerated areas develop. Occasionally the entire circumference of the anus will be ulcerated. Severe cases may result in the inabililty to defecate due to scarring or strictures or incontinence due to sphincter damage. A digital rectal exam is usually needed to determine the complete extent of the disease.

Treatment of perianal fistulas used to be exclusively surgical with excision of affected tissue and treatment with cauterization of the tissue with chemicals, electrocautery or cryotherapy as mainstays of therapy. Surgery is still occasionally needed for some cases but recent studies have had encouraging results with immunosuppressive therapy. Current recommendations include stool softeners, topical cleansing of the tissues, systemic cyclosporine, ketoconazole, prednisone or some combination of these along with a diet change to a low or novel antigen diet. This approach has been very successful in minimizing the lesions associated with this disease and some cures have been achieved. Prolonged medical therapy is often needed and relapses can occur. Some cases do not respond to medical management or only partially respond and surgery may be indicated. Removal of the anal sacs when involved is sometimes necessary. Other surgical options include excision of diseased tissue, tail amputation, cauterization of tissue beds and in severe cases a radical excision and rectal pull-through.

Long term prognosis is guarded as many dogs experience recurrence despite therapy and potential complications can be severe. These can included anal stenosis, incontinence and persistence of clinical signs.