Issue Description Canine anal furunculosis (perianal fistula) is
a formation of an abnormal channel between the anal canal and the skin
surrounding the anus. The continual discharge of watery pus from the
fistula can irritate the skin and result in itching, discomfort and
pain. Other Names Anal Fistulae, Perianal Fistulae
Causes While the precise cause of the disease is
unclear, some German Shepherds seem to be unable to resist even
superficial infections which may arise in the skin. This may be the
result of an ineffective immune response resulting in predisposition
to the development of skin infections as a persistent problem.
Additionally, the conformation of the German Shepherd allows for the
broad base of the tail to remain in almost continual contact with the
anus, thereby spreading a thin film of feces over the perianal region.
Hence this is the site which is affected most frequently. Recent
evidence, however, points to an immune-mediated process as the
underlying cause of this disease.
The anal sacs (scent
glands) are usually involved in the disease process and are removed as
part of the initial treatment. It should also be emphasized that a
dog's predisposition to the development of Perianal Fistulas is
lifelong. Relapses, although uncommon, may sometimes occur even after
Symptoms It is most common in German Shepherd and Irish
Setter breeds. However, it has been seen in other breeds. Males
outnumber females by 2 to 1. Clinical signs are characterized by
multiple draining tracts and ulcers immediately surrounding the
rectum. Animals may present pain and spasm when attempting to evacuate
the bowels (tenesmus), difficulty in defecation and constipation.
Affected area is usually very painful. An association between perianal
fistulas and inflammatory bowel disease is suspected.
Clinical signs of anal furunculosis:
Pain or spasm when attempting to pass urine or evacuate the bowels
Passage of red blood through the rectum
Ribbon like stool
Increased frequency of defecation
Perianal pus-filled discharge and/or bleeding
Low tail carriage
Diagnosis Diagnosis is based on physical examination and
history. Sedation may be necessary to perform a thorough examination
since the condition can be very painful. Biopsy samples will confirm
Treatment In the past, treatment for perianal fistulas
included surgical ablation (removal of the fistula) or deroofing
(removal of the skin covering each tract). In general, surgery has
been replaced by the use of immunosuppressive drugs. The response to
cyclosporine, prednisone, and tacrolimus has been encouraging.
Cyclosporine is generally considered to be the drug of choice and is
typically used on a 16-week course of treatment. Surgery, once widely
used, is presently reserved for cases that involve the anal sacs or
for selective cases that do not respond to medical management.
Prognosis Regardless of the treatment used, the earlier
the condition is diagnosed and treated, the better the outcome. In
most cases the prognosis is guarded to fair, understanding that
recurrence is common. In more severe cases, and those involving
surgery, fecal incontinence is a major concern.