Perianal Fistula in Dogs

A fistula is chronic skin lesion that gets worse over time, eventually becoming a deep, weeping ulcer. Perianal fistulas in dogs occur near the anal opening. Perianal fistulas are a painful condition that can cause behavioral problems and other physical symptoms. Here's what you should know about diagnosing and treating this unpleasant canine skin condition.

Causes and Risk Factors for Perianal Fistula in Dogs

Vets don't know exactly what causes a perianal fistula, but they think that the ulceration process begins with inflammation in the glands near the anal opening. Inflammation leads to infection, which leads to the formation of abscesses in the area. Because the area under your dog's tail is warm, dark and damp, bacteria, and infections, flourish there easily.

Male dogs between the ages of five and eight years old are most likely to develop a perianal fistula. However, dogs of all ages can develop this condition. German Shepherds are most prone to perianal fistula, most likely because they have more glands in the anal region, or because they are more vulnerable to immune-related diseases. Other breeds prone to perianal fistula include:

  • Irish Setters
  • Border Collies
  • Spaniels
  • Bulldogs
  • Labrador Retrievers

Perianal fistulas are also seen in mixed breed dogs.

Symptoms of Perianal Fistulas in Dogs

If your dog has developed a perianal fistula, you may see ulceration and bleeding from the area near his anus. Ulcers can be tiny, or very large. They may spread along the tail or into the rectal tissue. There may be an odorous discharge.

If your dog has a perianal fistula, he may lick or chew at his anal opening excessively, or drag his rear end across the floor. He may experience diarrhea or constipation. He may loose control of his bowels, and he may excrete bloody stool.

Perianal fistulas can cause other physical symptoms in dogs, including weight loss, lack of appetite and lethargy. If your dog's perianal fistula is very painful, it could cause behavioral changes, and even aggression. Your dog may move differently and may stop lifting his tail. Chronic inflammation of the skin around the anal opening could cause it to darken.

Diagnosis and Treatment of Canine Perianal Fistulas

Your vet should be able to diagnose perianal fistula through a physical examination, but your dog may need to be sedated, since this examination can be painful. Your vet may take tissue samples for biopsy, to confirm that the lesion isn't cancerous.

Treatment for perianal fistula depends on the severity of the condition. Small fistula are treated by removing hair from around the ulcer, disinfecting the ulcer, and keeping it clean with frequent washing. Oral antibiotics may be administered if the fistula is severe. Treatment for seven to nine weeks usually clears up a fistula, but the condition can recur.

In the most severe cases, your vet may suggest surgical treatment. Surgery involves removing the diseased tissue. Cryosurgery, laser surgery and even amputation of the tail may be necessary. Complications involve anal scarring and fecal incontinence.