tpvets_logo.jpg (2726 bytes)TOA PAYOH VETS

Date:   14 February, 2013  
Focus: Small animals - dogs, cats, hamsters, guinea pigs & rabbits
Oro-nasal fistula
Case report written by intern: Erica Chai Hui Ling 

Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
Date:   14 February, 2013 
Be Kind To Pets
Veterinary Education
Project 2013-0131
This text describes the processes of how a vet diagnoses & treats a case of oral tumours with tooth root abscess and oro-nasal fistula in an older Chihuahua. These processes form part of the Standard Operating Procedures at Toa Payoh Vets.





Owner noticed that the dog had swelling on the right side of the cheek for more than two weeks and later brought the dog to Toa Payoh Vets.

The patient: Chihuahua, Male, 10 years old, Singapore

There was swelling on the right side of the cheek however the appetite was still normal. The swelling had been there for more than two weeks. It seems like the old dog had oro-nasal fistula and tooth root abscess.

Life has not ended for this old dog as it was given a second chance by its owner. He had once been abandoned and later he found home with this kind hearted Singaporean who flew him all the way from Australia. He had journey far to reach his home sweet home.

The dog’s mouth is seldom examined by most dog owners and bad breath is usually tolerated by many Singaporean dog owners. They also seldom pay attention to the mouth part of their pet as long as the dog is eating without a problem.

Dental check up is not usually done and tartar will usually build up and rotten teeth fall off. Many owners are not bothered or are ignorant that dogs also need to have regular dental check up and dental care. However, the younger generation of Singaporeans are better educated and more concerned about the welfare of the old pets.

Back to my case.

One fine day on late January 2013, the owner of a male, 10-year-old Chihuahua noticed a swelling on the right cheek and brought it to Toa Payoh Vets.

At Toa Payoh Vets, Dr Daniel Sing was on duty. I was present. 
“This looks like a case of tooth root abscess as you can see that the teeth are rotten and filled with tartar. There may also be oro-nasal fistula. It is an abnormal communication between the oral and nasal cavities involving the soft palate, hard palate, premaxilla, or the lip” said Dr. Daniel.

Is it a case of tooth root abscess and oro-nasal fistula?
“So what are the treatment options available?” asked the owner.   
“For this case, we would recommend to go through surgery to remove all the affected teeth and clean the abscess” explained Dr. Daniel.
“But then how would my dog eat without teeth” the owner said.
“Don’t worry, the dog can eat soft canned food or even boiled chicken breast and porridge”
The financial costs and risk must be explained fully before any operation is done. But the owner must give his consent and that is where personality and financial conflicts come in. He must also be aware of the risk involve especially in older dogs. 

Blood test

Health screening is strongly advised before anaesthesia and surgery for all patients, esp. in the older dog.

Anaesthetic risks are much higher in old dogs. There is always the possibility that the older dog may die on the operating table. When the owner hears that the dog may die on the operating table, he may decide not to get the surgery done. Some deem the vet incompetent and consulted another vet. A health screening should be suggested by the vet to let the owner knows whether the risks are high or not.

"I advise a blood test to screen the health of the Chihuahua," Dr Daniel said.  The owners must consent to take the anaesthetic risk if they give permission for the surgery as in this case. No surgeon can guarantee zero risk in any anaesthesia, whether in people or animal.    

The total WBC 16.6 (normal 6.0-17.0). Neutrophils 50.8%, Lymphocytes 19.2%, Monocytes 24.6%, Eosinophils 1.1%, Basophils 4.2%. The platelets count is 520 which is slightly above normal (normal 200-500)
This blood test indicates that the liver and kidneys were functioning normally.
"OK," the owner consented to the surgery.

Antibiotics were given to the dog.
IV anaesthesia without Intubation.   

Anaesthesia. What type? IV, gas or both? IV anaesthesia is shorter acting than gas anaesthesia. Intubation (a breathing tube connects anaesthetic gas and oxygen to the dog) is usually done in dental extraction.

After the dog had been anaesthetised, I discover that there was a big tumour about the size of palm size dough growing from the soft palate. This tumour occupied the whole oral cavity and the plan now had changed. We had to remove the tumour and the teeth as well. Therefore we can’t intubate the dog as the tumour is obstructing the endotracheal tube.

“Call the owner and inform him about the tumour and the plan to remove it and ask for his consent." The owner gave his permission to proceed and the surgery continued.

Dormitor IV at 25% of calculated dosage for young healthy dog was sufficient for electro-surgical excision. Dental extraction was done after that.

The old dog survived the anaesthesia and that was what mattered most for the owner. It is not always possible for every old dog to survive anaesthesia during surgery. Therefore it is wiser to remove the tumour when it is smaller and when the dog is younger.


“Is the soft palate tumour cancerous or not?” the owner asked.
“Nobody can tell from the physical appearance,” I said. “The tumour needs to be analysed by the laboratory and the tumour cells can be seen under the microscope if there are any. This is the process of histology. Do you wish to get the tumour sent for histology?”
It is best to get the owner’s permission to send the tumour for histology to determine its state, as some owners may have budget constrain or do not wish to spend more money.


It is unprofessional to give medication to the owner to treat the oral tumour as some owners may insist on having them as an alternative to the high risk of anaesthesia during surgery as it will not disappear.
Electro-surgical excision of the soft palate tumour including extraction of molar teeth.
“The tumour can be removed from its stalk by using electro-cauterized to avoid losing too much blood,” said Dr. Daniel. Then after removing the tumour, the dog started to wake up from anaesthesia, so it had to be gassed with Isoflurane. When it was down, Dr. Daniel proceeded with dental extraction of the molar and drainage of the pus.

Histology Lab Result

The result of the histology came out and the nodule is covered by squamous epithelium with overlying parakeratosis. At the centre, there were irregularly-shaped trabeculae of woven and lamellar bone. There is no evidence of malignancy. So this is good news for the owner is it was not cancerous.


The final diagnosis from the histology is ossifying fibroma mass, with tooth root abscess and oro-nasal fistula. The dog was put on antibiotic and two days after surgery it was allowed home.



Tips & Advices:

Post surgical management.

1.    Owner need to come back for review every 3 months for the next 12 months. Owner needs to be advised and reminded by the vet but this is seldom done by me.
2.   The mouth of older dogs must be checked by the owner daily and any mouth tumour can be removed when it is small. In this case, the whole oral cavity had been filled with the tumour. It could have existed for some months without the owner seeing it.
TIPS: old and unhealthy dogs (>5 years) must be given 25-50% of the calculated dosage of IV anaesthesia for younger dogs to lessen risks of heart failure.

Prepared by:

Er Erica Chai Hui Ling



4th-year veterinary student wrote the above case study as part of internship requirements. Interns learn and remember much more when they write case studies. In this article, the 25% of domitor and ketamine was actually 50%. The high % of monocytes in the blood test indicated a chronic inflammatory condition. This would likely to be due to the growing inflamed mouth tumour of the old dog. Surprisingly, there was no increase in total white cell count although the mouth was badly infected and the ossifying fibroma was occupying almost the entire oral cavity for a long time. A "spell check" is best done before submission of the article to me.

The article is at the blog:

A report written by me is at:  

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