Dr Richard A S White
BVetMed, PhD, DSAS, DVR, FRCVS,
RCVS Specialist in Small Animal Surgery
Diplomate, American College of Veterinary Surgeons
Diplomate, European College of Veterinary Surgeons.

INTRODUCTION
WHAT IS ANAL FURUNCULOSIS ?

Anal furunculosis (AF), sometimes referred to as perianal fistulae (PAF), is an
immune-mediated syndrome encountered most frequently, although not exclusively,
in the German Shepherd Dog. It is characterised by areas of chronic infection and
ulceration involving the tissues around the anus with often unseen but deeply
infiltrating fistulous tracts which underrun the skin.
Additionally, many patients will have accompanying disease affecting the intestinal
tract which often manifests itslef as lower bowel inflammatory disease (colitis). In
most cases the dog's predisposition to the disease may be lifelong and there is
probably no long term ‘cure’ for the condition.

WHAT CAUSES THIS DISEASE ?

The precise cause of the disease still remains unclear but it is likely to be the result
of several factors the most important of which seems to be:

An abnormal immune response which can lead to a number of related
conditions including anal furunculosis, lower bowel inflammatory disease
(colitis) and possibly, a range of diseases, including skin problems.

Other factors which have been implicated but are probably of limited importance in
the development of perianal lesions include:

The anal sacs (scent glands) seem to be involved in causing the disease in
some cases and they may need to be removed if they are diseased.
The conformation of the German Shepherd allows the broad base of the tail
to remain in almost continual contact with the anus and is responsible for
spreading a thin film of faeces over the perineal region.

WHAT ARE THE SIGNS OF AF/PAF ?

Most dogs with only the anal lesions of AF/PAF will show few signs apart from
licking in the anal region. In a few very advanced cases the damage and scarring of
the muscle around the anus may be severe enough to prevent normal dilation of the
anus.
However, most dogs which show signs of difficulty when defaecating are probably
suffering in fact from concurrent lower bowel disease and these signs are only
unlikely to be the result of AF/PAF alone. The lower bowel disease may need to
be treated and controlled before treatment for AF/PAF can begin. These signs
usually respond to suitable dietary management (hypo-allergenic diets) although a
few may need specific medication.

HOW IS AF/PAF TREATED ?

Until we have a clearer understanding of the causes of the disease it is unlikely that
we will have a 'cure' for every dog with this disease. However there are a number
of options which may help to resolve some lesions.

Dietary Management: It is very important to control any abnormal symptoms
associated with the bowel (e.g. : loose motions, straining to pass motions, blood in
motions etc.). This may entail laboratory investigations, dietary changes and
medication. Many dogs have dietary hypersensitivity and finding a hypo-allegernic
diet is very important. This can be formulated at home using protein sources such
as fish, mutton, chicken and carbohydrate sources such as potato, rice, pasta.
Alternatively, there are many commercially-available hypo-allergenic diets - these
are usually complete diets and are often more convenient.

Medical Management: At the present time we do not have any consistently-
effective drugs for controlling the underlying predisposition to AF/PAF but
immunosuppressive drugs which modify and ‘damp down’ the immune system
(e.g.: prednisolone, cyclosporin) have been shown to resolve lesions in many cases.
Prednisolone is a relatively cheap drug which is widely available. It is has a number
of well-recognised side-effects and is only mildy immunosuppressive. Cyclosporin
is a very effective immunosuppressive drug which is used to control tissue rejection
after organ transplantation. Unfortunately, although it often brings about resolution
of the AF/PAF problem it is an extremely expensive drug.
It must be emphasised that neither drug can be regarded as producing permanent
or outright cure.

Surgical Treatment: Surgical removal of the infected tissue followed by
reconstruction of the surrounding skin produces very worthwhile results in many
cases and, together with dietary management of lower bowel disease, remains the
main treatment for many cases of AF/PAF.

WHAT POSTOPERATIVE CARE IS NEEDED ?

Surgery for AF/PAF is normally performed on an outpatient basis and most
patients are discharged on the same day as surgery providing that they have
recovered satisfactorily. In the case of extensive surgery your dog may benefit from
a short period of hospitalisation.

After surgery your dog will need :

Suture removal: The surgical wound should not otherwise require any
special attention and your veterinarian will be able to remove the sutures
after 10 days.
Dietary management: Unless a change of diet has been discussed as part
of your dog's treatment please do not alter the diet during the postoperative
period since this may induce diarrhoea and straining when passing the
motion.
Follow up: It is important that once treatment has begun your dog should
have a check-up after approximately 6 weeks.

WHAT IS THE PROGNOSIS FOR DOGS WITH AF ?

It is difficult to predict at the time of the initial consultation how individual cases will
respond to treatment. A more useful view can be obtained :

After a surgical exploration has been performed.
Once the result of surgery is reviewed 4-6 weeks postoperatively.
Lesions will eventually resolve in the majority of dogs which undergo surgical
treatment. However, some of these dogs will need more than one operation
and it is important that they are re-presented regularly for their check up to
minimise the risk of relapses.