Warning: Some of the photos used in this blog may disturb sensitive readers.
A fistula is simply a communication between two areas that would not occur naturally. There can be fisulas that communicate between a dog's anal sacs and the outside world, between a cow's rumen and the outside world and inside a dogs mouth we can have fistulas that communicate between the mouth and the nasal sinus. The mouth and nasal passages are typically separated by a layer of bone and the tissue lining the mouth and nasal passage. When a tooth becomes chronically infected, part of the body's response is to break down the bone surrounding the tooth. Periodontal Disease When the bone is broken down sufficiently a communication occurs between the mouth and nasal sinus. This leads to food material, water and oral bacteria being transferred to the nasal passage from the mouth. This can lead to sinus infections, sinus inflammation and even pneumonia. These need to be repaired surgically. The surgery is difficult and often has to be repeated due to the large defect we are trying to close with a limited amount of tissue.
This was a recent oronasal fistula repair that happened here at Riverside Veterinary Care, the patient was a Dachshund, this breed is prone to oronasal fistulas. In fact this dog had two, both were the upper canine teeth. The most common tooth for an oronasal fistula is the 4th premolar or Carnassial tooth on the upper jaw.
The picture below is after scaling and polishing and was taken during our charting of the mouth. We go around each tooth and obtain gingival sulcal depths to get an idea of how much active periodontal disease we are dealing with in each mouth. In this case there was a large defect on the inside of the canine tooth.
You can't see the defect just looking at the tooth and would have missed it if only the outside of the tooth was charted. Even on the x ray it can be difficult to see that anything is wrong.
If you look closely at the outline of the big tooth on the left and compare it to the second tooth to the right of that tooth, the outline of the canine tooth is much fuzzier and even appears to be eaten away in some spots. Still, looking at the picture of the tooth below you really can't tell that anything is wrong here.
When I insert a red rubber catheter into the spece behind the tooth however, I can get it to travel out the nostril. I would only do something like this while the pet was completely anesthestized and then only to illustrate the fistula.
I have already given this dog an injection of a local anesthetic and have discussed my findings and plans (including the pictures and the red rubber catheter) with the owner. I now make a long curving incsion into the gums to expose the bone around the canine tooth.
I understand you don't look at canine alveolar bone everyday so you'll have to take my word for it when I tell you that this bone is irregular. The tooth was extracted and the infected tissue was removed. This left a large socket that did a lot of bleeding.
I then place a local antibiotic in the socket and close the defect after preparing the flap so that it rests loosely over the socket. Tension will cause these surgery sites to fail every time and because these surgeries require a second procedure almost half the time anyway I like things to go as smoothly as possible the first time. For that reason, I really take my time making sure my flap is perfect the first time. I use absorbable suture as this little Dachshund probably isn't going to want to let me in its mouth again anytime soon!
The patient went home on some pain medication, with an E-collar (the cone of shame) and will be coming back in 10 days for a recheck. I will let you know how everything went then!