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Dog: Perianal Fistula

General information

Other common/scientific names: anal furunculosis

Perianal fistula is a chronic, inflammatory disease in which painful, abnormal channels or tracts form between the skin surrounding the anus and the deeper structures including the rectum. These tracts drain oily secretions, pus and blood causing further inflammation and infection.

Causes

The cause of perianal fistulas is unclear but it is believed to have an immune-mediated component. Other factors thought to play a role are poor ventilation associated with low tail carriage, an increased number of sweat glands, secretions from the anal glands and feces accumulations all of which create a warm, moist environment for bacteria to multiply. Some studies have shown a link to a chronic inflammatory condition of the colon similar to Crohn’s disease in humans. German Shepherds and Irish Setters are more prone to this condition. Intact (non-castrated) males are more commonly affected.

Cardinal symptom

  • Scooting
  • Licking the anal area

Symptoms

Dogs with perianal fistulas will scoot or drag their rear end across the floor. These dogs will be seen licking the anal area excessively. The tracts can vary from small and superficial to large, deep crevices extending into the rectum. The area around the anus will be ulcerated, painful and have a foul smelling discharge. Straining to defecate, constipation and/or diarrhea are other symptoms. With severe cases, these dogs will be reluctant to move their tails and may suffer from weight loss.

Abb. GGDF7UAJ
Abb. GGDF7UAJ: Perianal Fistulas.
This is a photograph of a dog with perianal fistulas. Note the oozing inflamed skin around the anus.

Diagnosis

Diagnosis can be made from a physical examination; however, sedation may be necessary to properly examine the perianal area. The depth and extent of the tracts are noted and the rectum is examined digitally. The anal glands should be examined for impaction or infected anal glands. A skin biopsy can be used to identify cells and aid in the diagnosis if another condition is suspected.

Treatment

Management of perianal fistula can be frustrating and disappointing because these cases do not respond consistently to treatment. Therapy includes:

  • Antibiotics: Since the area is infected, oral antibiotics are usually prescribed at the beginning of treatment. Mild cases may respond to a topical antibiotic.
  • Perianal hygiene: Clipping of hair and cleaning the perianal area with an antiseptic shampoo.
  • Corticosteroids : Most cases will respond initially to corticosteroids, but as the disease progresses, these medications are less successful.
  • Immunosuppressive drugs: These medications have shown the best success for long term treatment. A topical immunosuppressive ointment has been used successfully. For cases that do not respond, an oral immunosuppressive medication is recommended. Unfortunately, these medications are costly and need to be given for several weeks. Some dogs will require lifelong maintenance therapy.
  • Surgery: Surgery is recommended for dogs that do not respond to medical therapy. The goal of surgery is to remove the diseased tissue. If the anal glands are involved, they are surgically removed also. Tail amputation may be help to improve the local environment. Complications of surgery include pain, stricture formation and fecal incontinence.
  • Cryotherapy: Liquid nitrogen is used to destroy the abnormal tissue.
  • Laser therapy: Laser is used to destroy the abnormal tissue.
  • Dogs that are thought to have concurrent colon disease may benefit from a hypoallergenic diet consisting of a novel source of protein such as rabbit, kangaroo, venison or fish.

Prognosis

It is important for dog owners to understand that perianal fistula is a chronic, relapsing disease that can be managed but rarely cured. Lifelong therapy and management is needed. As with most chronic diseases, early diagnosis and treatment has the best prognosis.

Prevention

Keeping the perianal area clean and dry can help prevent fistula formation. Castration is recommended.

Tips

Stools softeners can be used to minimize straining and pain with defecation.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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