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Summary
Perianal fistula is a relatively common canine disease that yields painfully infected tracts in the skin surrounding the anus.
Although a hereditary component is presumed due to certain breed predilections, the cause of the condition is considered multifactorial. Allergic skin disease, hypothyroidism, conformation-related issues (as when dogs hold their tails close to their anus), and immunodeficiencies each or all potentially play a role in the disease process.
Middle aged to older dogs (usually 7 or older) are most often affected.
Symptoms and Identification
Straining to defecate, perianal pain and bleeding, constipation, licking of the area and smelly, discharge are typical.
Diagnosis is typically a simple, straightforward affair in which age, breed, clinical signs and physical exam conspire to confirm the presence of perianal fistula. Rectal examination (under anesthesia, if necessary) is required in most cases.
Affected Breeds
German Shepherds are almost exclusively affected, although some setters and retrievers have also been reported in the literature.
Treatment
Perianal fistula is a frustrating, difficult-to-treat disease. While medical and surgical treatments have both been described, both approaches can be insufficiently helpful for a great many dogs.
Medical management typically involves the use of drugs that interfere with the inflammatory response. Cyclosporine and tacrolimus have both been employed successfully. Antimicrobials and antiseptics are often administered as well by way of treating the secondary infections almost always present.
The surgical approach to perianal fistula management relies on the removal of the tracts, preferably before the disease becomes severe. More than one procedure is sometimes required. Tail amputation has also been described as potentially helpful for dogs whose conformation has been deemed a major contributing cause of the disease.
Veterinary Cost
The expense associated with drugs and or surgery can be devastating to owners whose dogs suffer this condition. The drugs used to treat this condition (usually required long-term) are often prohibitively expensive at $200 to $500 a month. Surgical interventions are also expensive, more so because these surgeries are almost always undertaken by highly trained, board-certified veterinary surgeons. $2,000 to $5,000 would be the typical cost for such a procedure.
Prevention
Although it's difficult to say how large a role inheritance plays, it's not recommended that affected dogs be allowed to propagate this trait.
References
Bojrab, M.J. Surgery of the anus (Proceedings), Apr 1, 2008 CVC PROCEEDINGS.
Patricelli, A. J., R. J. Hardie, et al. (2002). "Cyclosporin and ketoconazole for the treatment of perianal fistulas in dogs." J Am Vet Med Assoc 220(No 7): 1009-1016.