Perianal fistulas are an extremely painful medical condition of the anal region of dogs. As the name describes, this condition involves infection in the skin and surrounding tissue of the anus. ‘Peri’ means around, the anus, while a fistula is a tunnel in the skin that connects an area of infection to the skin or glands. This condition is characterised by very smelly draining sinus tracts in the skin around the anus and sometimes the deeper structures beneath the skin up to the rectum. 

What does a perianal fistula look like?

The disease usually presents as smelly, longstanding, non-healing pussy tracts and holes around the anal region. The wounds tend to be raw and painful, resembling ulcers. Affected dogs are usually in excruciating pain, evidenced by excessive licking and biting at the anal region. Due to the great discomfort, the behaviour of the animal might change to being aggressive – especially when an attempt to handle the tail is made. They may even avoid actions such as sitting. Aside from the physical infection, these dogs may also experience digestive tract problems such diarrhoea or constipation. Faeces might have a bit of blood or mucus covering it as it passes, often accompanied by pain and discomfort. Affected animals usually feel quite miserable and some may show reduced appetite and being less active than usual.

What causes a perianal fistula?

The exact cause of this condition is unknown. However, there are a number of theories as to why it develops. Poor air ventilation around the anus due to thick, bushy and low-hanging tails is thought to be a major predisposing factor. Bushy and fluffy tails, when paired with extra skin folds around the rear end, create a moist environment conducive for the collection of dirt and faecal material. Such a dirty environment favours infection and in some cases may lead to non-healing fistulas.  

Another probable theory is that the condition is associated with underlying autoimmune conditions. One unproven theory is that allergies may predispose some animals to the development of non-healing fistulas. Perianal fistulas are also thought to be a complication resulting from chronic anal sac (anal gland) infection or disease. A genetic link is also thought to exist given that certain lines of German shepherds seem to be affected more than others. 

Which animals are more likely to be affected?

The condition is often encountered in German shepherds and related breeds of dogs, and sometimes in Irish setters and the retriever breeds. Rarely will other dog breeds be affected.

Research has shown that the majority of animals that develop perianal fistulas are older animals, usually around seven years of age, but younger GSDs can also be affected. They also tend to be sexually intact (not spayed or neutered). 

What do I do if I suspect my pet has perianal fistulas?

If you have noticed any of the above-mentioned problems with your pet, it is highly recommended that you make an appointment to visit your vet. Perianal fistulas do not go away on their own and usually require thorough cleaning and antibiotic treatment as well as anti-inflammatories to manage pain and discomfort. This is not something easily managed at home.

What will the vet do if my pet has perianal fistulas?

Generally a diagnosis is reached based on the clinical examination findings in the typical breed of dog. Rectal examinations are also done in patients suspected to be suffering from this condition. Given the degree of pain and discomfort this condition causes, sedation might be required for a thorough physical examination to be possible. To reach an accurate diagnosis, the vet may collect tissue samples for histopathology in order to rule out other complicating factors. Samples for bacterial culture and sensitivity testing will be taken in order to give targeted antibiotic treatment.  

How are perianal fistulas treated?

Treatment of this condition could be through medical case management, surgical management, or a combination of both. Medical management includes the use of antibiotics to clear secondary infections, and immunosuppressive drugs systemically as well as topical ointments to reduce inflammation. Dosages of all drugs are case specific. With some patients, immunosuppressive drugs at low doses are continued for the rest of the animal’s life to maintain remission. It’s important to keep the perineum clean to ensure the dog stays healthy. The hairs around the perineum should be kept short so that there is adequate air circulation in the area. The perianal region should also often be cleaned with topical antiseptic to maintain high levels of hygiene. 

Nutrition is another aspect of medical management that improves treatment outcomes. Patients should be changed to a novel protein diet or a hypoallergenic diet. A hypoallergenic diet is beneficial since most sufferers have underlying allergic and autoimmune conditions. Pet owners would therefore be required to adhere to the strict conditions that come with feeding a novel diet. 

The affected pet may need surgery if medical management is not successful. It’s worth noting that surgery around the anus can result in unwanted complications, and it might actually be unable to treat the patient completely. Surgery is useful in removing non-healing sections, early treatment of small wounds, removing problem anal sacs, as well as removing malignancies in proximity to affected sites. Another surgical procedure, which could be beneficial to the patient, though controversial, is tail amputation. The logic behind tail amputation is that the perianal area will be exposed to air, reducing moisture in the area. 

My dog has been diagnosed with perianal fistulas – what now?

The mainstay of aftercare (ongoing management) is hygiene in the perineum region. The perineum must be kept clean, adhering to the instructions given by the attending veterinarian. For cases that require chronic medication, treatment must be continued with consistency to avoid unwanted setbacks. It is prudent to highlight that the chronic immunosuppressive drugs to manage this condition such as cortisone do come with negative side effects with prolonged use. It is critical to keep to the affected animal’s recommended diet. 

Advice to the pet owner

This condition can be emotionally taxing to the owner of a dog with perianal fistulas, due to the common recurrences and stubbornness to different therapies available. Research indicates that approximately 20% of affected dogs do not respond to treatment at all, while a significant percentage of patients might have recurrences. Treatment is protracted over several weeks to months, with the dog in significant pain. The pet owner is thus encouraged to prepare themselves mentally as well as having patience for the duration of case management. They must also stick to the aftercare tips religiously in order to decrease the chances of recurrence. Thus the pet owner must have joyful tenacity in the whole treatment journey of their pet. At times the chronic medications used for perianal fistulas are in short supply in the market, thus a good degree of organisation will also be demanded from the owner so that the patient does not get to a point where they run out of supply. 

Constant liaison with the vet is therefore strongly encouraged throughout the whole treatment journey. 

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