99. Sunday's highlighted case: Oro-nasal fistula 15 years old

Date: Sunday, Jun 13, 2010

Case on a Sunday: Maltese X, Female, Not Spayed, Weight 5.5 kg. 37.9 deg C. Active and eating.

Complaint: Pus below right eye. Rubs right side of face onto bed sometimes.
3 Owners: 2 young men and a lady all around late 20s.

History: Had consulted Vet 1 who prescribed oral Baytril 50 mg antibiotics 1/2 tablet two times a day from May 16, 2010. But the owners gave the dog 1/2 tablet one time a day as they deemed that the dog would be overdosed. The pus in the facial wound disappeared after 2 days. However the medication finished after 20 days and pus re-appeared in the wound below right eye during last 2 days.

Diagnosis: Owners knew the diagnosis of oro-nasal fistula as they had researched the internet.

Prognosis: "It is very high risk and the dog may die on the operating table," I advised the owners to get a blood test done to screen her health. The vet must inform the owner and the owner is free to reject the advice. Since the owners did not want a blood test, it was hard to estimate the anaesthetic risk. In any case, such an old dog would be very high risk.

I checked the dog's heart. It was OK. The dog was in good bodily condition and had good body weight. So I gave a 50:50 chance of success. Usually the chances are less than 50%.

Pre-op:
1. Antibiotics IV with the drip or return after 5 days of antibiotics for surgery.
The owners chose the IV drip.

Anaesthesia:
1. Isoflurane gas by mask. Intubate. This dog was not able to sleep fully. When a loose tooth was extracted, he would wake up partially and moved. So, I took out the endotracheal tube, put on gas by mask and repeat the intubation. After 3 episodes, I decided just to give isoflurane by gas mask. 6 teeth extracted including the right and left premolars. Dental scaling done. If the dog had been sedated, he would have a smoother anaesthesia. However, sedation may cause low blood pressure or kill the dog and so in this case, I used isoflurane gas only as it is much safer for an old dog. This would also take a longer time to anaesthesize the dog.

Surgery:
1. IV drip with antibiotics baytril was given before surgery. The dog bit off the drip line before surgery.
2. Loose teeth were extracted. I was surprised to see thick pus actually lodged in the roots of the right upper pre-molar. Like a wallet full of cheese. I used the forceps to scrape out the light yellowish pus.

Post-Surgery :
1. Two hours later, the owners came to bring her home.
2. No solid food for the next 3 days so that the big holes from the extracted teeth would close . Just give soup, milk or honey water for 3 days.
3. Antibiotics for 20 days.

This dog should live to a ripe old age of 20 years. "No more white coat," the young man said. "As she grows older, her coat colour became brown." I asked: "Did you use yellowish shampoo?" "Yes," the owner said. "The shampoo colours the coat over the years," I explained. "If you use a "white-dog shampoo", the coat will not become stained yellowish brown for a white coated dog."

All ended well for this well loved dog. I asked the young man to sit on a chair and hold the dog and opened her mouth. The dog kept moving her head. After 15 minutes, he could open the mouth and was surprised to see a bleeding hole over 1 cm in size where the right upper premolar was extracted. "I thought the pus come from the front teeth or the fangs," the young man was indeed surprised that the source was from the root of the premolar 4. Fortunately, he could open the dog's mouth so that he could see the hole and I could snap a picture to educate readers.

This must be one of the oldest dogs in Singapore to have an oro-nasal fistula. At this age, most teeth had dropped off.

UPDATE ON JUNE 14, 2010
The owner phoned to say that the dog was coughing. "This coughing was due to the irritation of the throat during the many times of intubation, " I said. "It should clear up within 2 days. Continue giving the antibiotics." No further news from the owner after this.
VET PHARMACOLOGY FOR VET STUDENTS
Baytril 50 mg (5mg enrofloxacin/kg bodyweight) is advised by the manufacturer to be 1 tablet per 10 kg bodyweight once daily or as a divided dose twice daily for 3 to 10 days with or without food.
For this dog weighing 5.5 kg, the dosage should be 1/2 tablet once daily or 1/4 tablet 2x/day. It seems that Vet 1 advised double dosage at 1/2 tablet 2x/day.

In any case, the owners felt that the dog did not need so much antibiotics. So they gave 1/2 tablet 1x/day (which is what the manufacturer recommended) from May 16 for 20 days till Jun 4, 2010.

Baytril was effective as the pus discharge occurred only on Jun 11, 2010 (2 days ago). "What did Vet 1 advised?" I asked the owner. "Vet 1 said that the wound would not be going to heal and would come back again. She advised dental work after the antibiotics."

In this case, the owner was informed about the need for "dental work" and that the wound would return again. They were also informed about the high risk of anaesthetics and had cancelled a dental scaling one year ago. However, in the case of oro-nasal fistula, they had no choice. They were fortunate that the old fawn coloured Maltese X survived.
What is an oro-nasal fistula?
It seems that the internet had much information for the young owners, and so I did not need to elaborate. Basically, it is a wound in the face connecting the sinus to the roots of the pre-molar 4 tooth. It is also known as carnaissal tooth abscess.




A non-healing facial wound below the eye

Extraction of the carnaissal tooth is the only solution to cure the condition known as oro-nasal fistula or carnaissal tooth abscess