Overview:

A Perianal Fistula is an infected track or tunnel between the deep tissue of the anal area and skin in dogs. The contusion may first emerge as small holes in the skin that ooze fluid, however the severity may vary. This results in these holes becoming broader and deeper encapsulating the whole anal area. This condition can affect any dog this infection is mainly found in German shepherds. The main contributing factor in German shepherds is the way in which they carry their tails. This is generally low and between the bones of the hip. The tails usually cover the anus. There is much discomfort coupled with severe pain with this condition. An uncontrolled Perianal Fistula can radically decrease quality of life in a dog. Co-exiting chronic diarrhoea may also be caused by an inflamed bowel disease; relatively the conditions can be associated with one and other very closely. This condition is often equated to Crohn’s disease in humans.

Signs and Symptoms:

  • Painful defecation
  • Straining while excreting
  • Constipation
  • Diarrhoea
  • Mucus or bloody stools
  • Licking or biting of the anal area

The severity of the pain in the area may cause your pet to be agitated and restless. Dogs may make sounds indicating pain every time they need to defecate. Affected dogs may struggle and some may try to bite if their tails are raised.

Diagnostics:

It is necessary to have a full physical check-up. The physical must include a digital rectal examination, the reason being that the infection or blockage of anal sacs can cause Perianal fistulas. Sedation may be required in cases of severe pain. Tissue or cell samples may be collected from the fistula or anal sacs for a microscopic examination (aspirations, histopathology, cytology) or bacterial cultures and sensitivity.

Figure 1: Small perianal fistula (arrow).

Figure 2: Severe perianal fistulas in a German shepherd.

Treatment:

Both medical and surgical treatment are used in conjunction with each to lessen the opportunity for a reoccurrence as the infection has proven to return to 80 percent or more of dogs, dependent on the course of treatment the dog has undergone. The medical side of the treatment is generally performed by a board-certified internist or veterinary dermatologist.

Treatment may include the following

  • A dietary change to a specialised protein diet
  • Metronidazole or similar antibiotic
  • Oral immunosuppressive drugs/ anti-inflammatory, such as azathioprine, prednisone, cyclosporine
  • Tacrolimus or similar topical immunosuppressive medications

Surgical treatments are usually performed if:

  • When contusions/lesions are small,
  • Remove of anal sacs that are affected
  • Fistulas are completely healed after medical treatment , or
  • To make dogs more less uncomfortable in recurrent or very severe cases

Dead (necrotic) tissue associated with the fistulous tract may require surgical treatment to promote healing. Both laser treatments and cryosurgery are commonly used in this instance. In Cryosurgery the affected tissues are frozen using a special probe. These frozen cells die and are usually shed, thus allowing further healing to take place. The pain is usually lessened straight away after surgery, leaving your dog in a lot less discomfort. Lasers have a similar effect to that of freezing, where is kills the lining of the fistulas and the affected area will heal slowly over time.

In certain cases an amputation of the tail is required. This procedure facilitates the healing of existing fistulas and decreases the likelihood of a recurrence; it may also allow easier cleaning of the area and aeration of the site.

Figure 3: Liquid nitrogen is applied to the opened fistulas, producing clouds of cold air.

Figure 4: An ice ball (arrow) forms where the tissue is frozen. The frozen tissue dies, develops a scab or crust, and eventually falls off, leaving a healthy wound bed that will eventually close on its own.

Aftercare and Outcome:

There will be raw, open wounds for a number of weeks after a Cryosurgery and laser surgery. This requires daily cleaning to remove bacteria, dead tissue and faecal matter from the area. For dogs with severe pain during defecation an addition of stool softeners or laxatives such as lactulose; can be used in the treatment. In order to prevent self-mutilation, the dog may need an e-collar to wear until the area has healed properly.

Perianal fistulas may be treated as a chronic condition requiring medical management for the duration of the dog’s life cycle this may be inclusive of drugs and novel diets to suppress the immune system and improve bowel function. As with much medication drugs used for treatment of perianal fistulas can have serious side effects. They should not be used in conjunction with other medication unless specifically approved by your veterinarian. If initial legions are detected in early stage the healing is usually quite good. However, the recurrence of this malady is common, especially in dogs with medium to severe disease. Loss of control over when or where a dog may defecate (Faecal incontinence) can be caused by chronic damage to the perineal region due to Perianal fistulas or even after surgeries that affect nerves in the area.

Sadly, there are no preventative measures for Perianal fistulas as yet. Special diets decrease the chances of allergic or inflammatory intestinal diseases which are commonly associated with development of Perianal fistulas. Heredity may be some cause for the development of this disease, therefore the risk of suffering with this disease being higher in German shepherd breed. Dogs with Perianal fistulas should not be used for breeding to reduce the risk of the disease being passed on to offspring.