Perianal Fistula in Dogs

Tunnel-like formations in your dog’s skin and deeper tissues in the surrounding area of your dog’s anus are called perianal fistulas. These lesions can be minor or more serious; they begin as small holes in your dog’s skin and then can become wide and deep and can ultimately surround your dog’s anus in its entirety. This condition is most likely to occur in German Shepherds, though it can happen in any breed. 

Perianal fistulas can cause a great deal of pain and discomfort in your dog. Dogs that experience a perianal fistula may also have chronic diarrhea as a result of inflammatory bowel disease; it is thought that these two conditions may be connected.

Perianal fistula, which is also known as anal furunculosis, occurs when a dog experiences chronic lesions around their anus that worsen, leading to deep ulcers that drain and are painful to the dog.

Should your dog have a perianal fistula, you may observe the following:

• He is experiencing pain when defecating
• He is struggling to defecate
• He is constipated and/or experiencing diarrhea
• Mucus or blood in his stools
• Extensive licking and biting of his anus
• He may appear restless and cry out when he is about to have a bowel movement.
• Should you try to lift his tail he may struggle or bite.
• Low tail carriage
• A foul smell
• Irritability and even aggression can occur due to the severe pain dogs can experience 

Types 

A dog can experience a mild perianal fistula or his condition may be moderate or severe.

The exact reason that perianal fistulas occur is not fully understood. It is thought that the condition begins as inflammation of the sweat and oil glands that are in and around your dog’s anus. This then results in an infection of the area, which can then lead to abscesses that open and drain. The area under the tail and around the anus is warm and moist, which makes it easy for bacteria to multiply.

While perianal fistulas most often affect German Shepherds, they can occur in any breed of dog. German Shepherds often carry their heavy tail low between their hip bones, which will cover their anus; it is thought this may predispose them to this condition. Because German Shepherds are more often affected, genetics may play a role in the condition developing.

Should you notice any of these symptoms in your dog, you will want to schedule an appointment with your veterinarian. In addition to asking you for information regarding the symptoms you have seen in your dog and when you first noticed them, your veterinarian will conduct a physical examination. This will include a rectal exam because perianal fistulas may be caused by an infection or blockage of the anal sacs. Some dogs will need to be sedated in order for the exam to be conducted. Your veterinarian will obtain samples of cells or tissues from the anal sacs or fistula which can be looked at under a microscope or used for bacterial culture and sensitivity testing.

Your veterinarian will likely consider providing both medical and surgical treatments as 80% of those experiencing perianal fistulas will experience a recurrence of the condition. When the condition is relatively mild, your veterinarian may clip any hair in the anal area and cleanse the area with an antiseptic solution and then flush the area with water. Should the condition be more severe, treatment options include:

• Modifications in your dog’s diet (a novel protein diet)
• Antibiotics (for example metronidazole)
• A combination of oral cyclosporine and ketoconazole
• Administration of oral anti-inflammatory and immunosuppressive medications like prednisone (this has been less effective than cyclosporine and ketoconazole)
• Topical immunosuppressive medications

Treatment will usually take place for 7-9 weeks, though recurrence is typical once treatment is stopped, particularly in dogs with moderate disease.

Your veterinarian may also consider surgical treatment which will include removing any affected tissue, whether through freezing it, cautery or laser surgery. Anal sacs may also be removed during surgery. In some cases, the veterinarian may recommend removing the tail as it may help with keeping the area clean and aerated, which will assist with healing of current fistulas and decrease the chance that the condition will recur; this is done less often today.

Should a dog undergo cryosurgery or laser surgery he will have open wounds for a few weeks. These will need to be cleaned daily and dead tissue, bacterial and fecal material will have to be removed. Your veterinarian will likely recommend that your dog take stool softeners to help your dog not experience pain when having a bowel movement. An e-collar will likely be necessary so that your dog does not cause harm to the wounds.

The condition will often have to be managed over the course of your dog’s life, through diets and medication (immune suppressants). In cases where the dog experiences chronic damage to the perianal area, whether from the fistulas or after surgeries, it can impact the area’s nerves, which can cause fecal incontinence.

Perianal fistula can be expensive to treat. If you suspect your dog is at risk of perianal fistula, start searching for pet insurance today. Wag!’s pet insurance comparison tool lets you compare plans from leading companies like PetPlan and Embrace. Find the “pawfect” plan for your pet in just a few clicks!