Veterinarian-written / veterinarian-approved articles for your dog.

Perianal Fistulae in Dogs

Learn the causes of perianal fistulas in dogs.

Perianal fistulae are draining tracts in the tissue around a dog's anus. In most dogs, there is more than one such sore.

Causes of Perianal Fistulae in Dogs

It isn't known precisely what causes perianal fistulae in dogs. Some people believe there's a genetic component because over 80% of affected dogs are German shepherds. However, that might be more because of the way that breed is built, with a low-hanging tail and broad tail base that contribute to poor air flow under the tail. Shepherds also seem to have a higher concentration of sweat glands in the anal area than other dogs.

It is thought that perianal fistulae occur when sweat and oil glands around the anus become inflamed and then infected. Abscesses form in those glands and break open to drain—those are the visible oozing wounds. Often, anal gland infection preceded perianal fistulae.

There may also be an immune system component to perianal fistulae. The dog's immune system seems to overreact to the inflammation in the anal area, and that makes everything worse.

Signs of Perianal Fistulae in Dogs

Signs of the condition include:

  • Constipation or diarrhea
  • Excessive licking and chewing at the anus
  • Fecal incontinence
  • Painful rear end
  • Holding the tail down
  • Foul odor to the dog's rear end
  • Blood in the stool
  • Decrease appetite
  • Weight loss
  • Draining sores around the anus

Diagnosis of Perianal Fistulae

Diagnosis of the condition is made by seeing ulcers that ooze around the anus. A biopsy of the area can confirm the condition and rule out others, like cancer, rectal fistula, or chronic anal sac disease.

Treatment of Perianal Fistulae in Dogs

Medical therapy of perianal fistulae includes clipping the hair around the area to improve airflow, cleansing it gently every day, applying topical antibiotics, oral antibiotics, and giving immune-modulating drugs like cyclosporine and prednisone. Pain medications are also usually required. Some dogs, when indicated by other associated signs, are put on a hypoallergenic diet. The affected dog may need to wear an Elizabethan collar in the early stages of treatment to decrease self-mutilation of the area and allow it a chance to heal.

Surgery may be required in severe cases, but it can produce varying degrees of resolution.

This condition can be frustrating as it often requires ongoing management throughout the dog's life.

You May Also Like These Articles:

Megaesophagus in Dogs

Dog Anal Sacs

Why Does My Dog Stink?

How to Help Your Dog Get a Better Grooming

Disclaimer: This website is not intended to replace professional consultation, diagnosis, or treatment by a licensed veterinarian. If you require any veterinary related advice, contact your veterinarian promptly. Information at is exclusively of a general reference nature. Do not disregard veterinary advice or delay treatment as a result of accessing information at this site. Just Answer is an external service not affiliated with

Notice: Ask-a-Vet is an affiliated service for those who wish to speak with a veterinary professional about their pet's specific condition. Initially, a bot will ask questions to determine the general nature of your concern. Then, you will be transferred to a human. There is a charge for the service if you choose to connect to a veterinarian. Ask-a-Vet is not manned by the staff or owners of, and the advice given should not delay or replace a visit to your veterinarian.