PERIANAL FISTULA

About the Diagnosis

Perianal fistula is a disease of the tissues surrounding the anus. With perianal fistula, one or several draining tracts (open sores) develop in the skin directly around the anus. The sores are very painful and can be foul smelling. The condition tends to get progressively worse in affected dogs. German shepherds and Irish setters are the most frequently affected breeds, although the condition can occur in retrievers and spaniels as well. These breeds have broad-based tails or low tail carriage, and this body conformation is believed to contribute to the development of the disease. The main cause appears to be an autoimmune destruction of tissue in this area-the body's own immune system mistakenly identifies normal tissue as foreign and proceeds to attack and destroy it. In this case, the normal tissues surrounding the anus are misidentified and partially destroyed. Allergy to certain ingredients in foods may also play a role in development of perianal fistulas.

Early in the disease the only symptom may be persistent licking of the anal area. Other signs include straining to defecate, blood on the stools, discharge from the anal area, and constipation. The condition often is painful, such that the dog will usually not allow the tail to be lifted. A severely affected dog may be in such pain that it develops poor appetite, weight loss, and behavioral changes (e.g., aggression).

Because of the discomfort associated with the condition, your pet may need to be sedated for a thorough examination of the area. Diagnosis is made on the basis of the presence of specific lesions called draining tracts (deep sores) in the skin near the anus. Conditions with a similar appearance such as dog fight wounds, anal sac abscesses, and perianal tumors will be considered and evaluated your veterinarian. This sometimes requires a biopsy procedure for the submission of tissue for microscopic examination by a pathologist.

Living with the Diagnosis

Perianal fistulas are a chronic condition that can often be improved but rarely permanently eliminated. Treatment with medications (oral pills, wound care, etc.) may successfully control the condition, and lifelong treatment usually is necessary. Although surgery can improve this condition as well (removal of the affected tissue), the condition can reoccur after surgical treatment. It is also important to monitor affected dogs' vital functions, especially defecation. Some dogs with severe perianal fistulas that do not respond well to treatment are prone to developing problems with fecal incontinence or stricture (narrowing) of the anus. Considering the possibility of such complications but also the possibility of excellent control and an otherwise normal life, the long-term outlook for patients with perianal fistulas is guarded, and individual response to treatment varies substantially from one dog to the other.

Treatment

Treatment using medications only (no surgery) can control many cases of perianal fistula. First the area is thoroughly cleaned by your veterinarian while the dog is under anesthesia. Antibiotics often are prescribed to control an infection if one is present in the draining tract lesions. Orally-administered immunosuppressive drugs are used for controlling the underlying, immune-mediated basis of the disease. In addition, since a food allergy may be involved, a hypoallergenic diet should be fed, and specific types and ingredients should be reviewed with your veterinarian. Hypoallergenic diets on the market are not all hypoallergenic for all individuals, so selecting one is a careful issue that needs to be covered in detail during the veterinarian office visit to avoid choosing the wrong diet.
In severe cases or if the dog does not respond to medications and routine care, one of several surgical procedures can be used in an attempt to remove all diseased tissue. Possible complications of surgery are fecal incontinence due to damage to the muscles surrounding the anus, anal stricture due to scarring around the anus, and reoccurrence of the condition. In general, surgical approaches are falling out of favor as the benefits of immune-suppressive therapy become more and more clearly identified.

DOs

• Give all medications exactly as directed.

• Ask your veterinarian detailed information about how to properly wash your dog's hind end. This simple but critical aspect of treatment should not be painful to the dog or stressful to you. Points to be covered include what to use as a wash solution, what to use as a rinse, how often to do it, and what signs to watch for as reasons to stop.

DON'Ts

• If your dog has perianal fistulas, don't handle his/her tail if doing so seems painful.

• Don't expect a short course of treatment. Some dogs with perianal fistulas require ongoing treatment for the rest of their lives, whereas others have complete improvement and only occasionally experience relapses.

When to Call Your Veterinarian

• If your dog has not defecated in 24 hours or more. The pain of defecation in dogs with severe perianal fistula is such that they can become constipated, which leads to even greater pain when trying to pass stool. Therefore, if normal stools are not being passed, check for constipation.

• If your dog feels poorly (decreased appetite, sluggishness/lethargy, etc.). These symptoms can occur from complications of perianal fistulas (such as infection) or may be related to medication problems, requiring an adjustment.

Signs to Watch For

• Persistent licking of the anal area.
• Foul odor from the tail area.
• Straining to defecate.
• Fresh blood in the stools or dripping from under the tail.
• Reluctance to allow lifting of the tail due to pain.

Routine Follow-Up

• Dogs treated either with medications or surgery should be examined periodically to monitor the condition. Dogs taking immunosuppressive drugs need periodic monitoring for possible side effects of the medications.