Fistulas in Dogs

The Veterinary Dictionary definition of fistula is "any abnormal, tube-like passage within body tissue, usually between two internal organs, or leading from an internal organ to the body surface." Fistulas are also described as "ulcerous channel-like formations that may be caused by injury, abscess or infection, and that penetrate deeply enough to connect with another organ or permeate the skin" (Columbia Encyclopedia).
Many types of fistulas affect people and animals, but for dogs, the most common, serious and least understood is the perianal fistula.

Perianal Fistula

Perianal fistula, considered an autoimmune disorder, causes the dog's immune system to attack its own tissues from the inside out, leading to internal masses and painful external lesions. The disease probably begins near the intestines and unseen portion of the anus, and in response to this "threat" the dog's immune system attempts to eliminate the internal disease by forming tube-shaped structures, called fistulae, that eventually exit through the skin in the vicinity of the dog's anus. It is usually only when the external openings or abscesses are visible that you realize something is wrong.
Some signs and symptoms of PF are: straining to defecate, pain while defecating, failing to retain feces long enough for it to form, resulting in soft feces, frequent licking of the anus, coprophagia (eating feces), and visible, painful abscesses in the anal area.

Research

Despite years of research at veterinary hospitals, universities and laboratories, scientists have not yet determined the precise cause of perianal fistulas. It is known that German Shepherds account for 80 percent of diagnosed cases and that breeds such as Irish Setters and Leonbergers are also over-represented in the numbers of dogs suffering from this condition. New research has shown that many of the fistulas develop secondary to autoimmune issues and to underlying food allergies.
British veterinarian Trevor Turner, wrote that over the years "treatments of Perianal Fistulas have varied from tail amputation to cauterization of the fistulae through surgery to cryosurgery (applying freezing liquid nitrogen to the diseased tissue) and laser therapy. It is a sure sign that we do not know the cause and therefore cannot design a logical treatment when such variety of `cures' is on offer."

Treatment

For the past 8 years, treatment has shifted from surgery, which previously included tail amputation, to using various medications to regulate the immune system. Rather than focus only on removing the fistula itself, with procedures that seldom work without relapse or problematic repercussions, many veterinarians now recommend a combination of cyclosporine (modified) and ketoconazole, along with a hypoallergenic diet. This treatment has been more successful than surgery in shutting down the immune system to prevent it from attacking the tissues around the intestines and anus long enough for the fistulas to heal.
Because immunosuppressant drugs may have serious side effects and leave dogs open to infection, they are seldom used long-term, although some dogs have remained on them for long periods of time and have done well. Some people whose dogs have perianal fistulae use prednisone instead of cyclosporine, in part because it is far less expensive and some believe it may work faster and have fewer short-term side effects, though long-term use of high dosage prednisone is strongly discouraged. Many vets also prescribe an antibiotic in conjunction with the immunosuppressant to prevent infections.
Tacrolimus cream is an immunosuppressant with predominantly topical effects that is applied no more than once a day around the anus, though not directly into the fistula openings. Continuing tacrolimus application after the cyclosporine has been cut back or eliminated has allowed some dogs to remain in remission longer.

Diet

Most dogs with perianal fistula have other immune system problems and since the goal of this aggressive and expensive treatment is to get the immune system to stop attacking the dog's own tissues, it is essential to try to eliminate or treat anything else that triggers an attack. Allergies, food sensitivity and other gastrointestinal problems are common in dogs with perianal fistula, with German Shepherds at the top of the list of dogs who react negatively to specific proteins or grains. If your dog is diagnosed with perianal fistula, one of the most important things you can do is to introduce a grain-free food composed of only one protein that you know your dog has never eaten before. Staying with this diet will reduce the possibility that food sensitivity is contributing to keeping the dog's immune system active, preventing healing, and possibly creating new fistulae.

Prognosis

Your dog's quality of life can be improved significantly if you are able to follow a protocol of watching your dog for signs of flare-ups, keeping the anal area clean, medicating with cyclosporine, ketoconazole and feeding a single protein, grain-free diet, either canned, dry, raw or cooked. Perianal fistula is a manageable chronic disease, not a death sentence, but it is confusing, frustrating and painful for your dog, time-consuming and very stressful. The treatment is extremely expensive, and for some, impossible to afford, so you need to trust your veterinarian, learn what you are dealing with and investigate alternatives.
To better understand and cope with perianal Fistula, do research, ask questions, get second opinions and, most important, communicate with others who are dealing with the same disease. You can join an online group, such as the knowledgeable PF-L Yahoo! Group (See References) that offers information, experience and support, and they will help you and your dog as you struggle with this condition.

References

• Perianal Fistula Support & Information
• Anal Furunculosis by Trevor Turner
• Important Information Pertaining to PFs by D.J. Hensch

Resources

• Chronic Inflammation of the Anus, Rectum or Perineum Region in Dogs: Perianal Fistula in Dogs
• Anal Furunculosis (2) by Trevor Turner