The hard palate is located in the roof of the mouth that is made of a thin layer of bone and covered with a mucous membrane that separates the oral cavity (mouth) from the nasal cavities. An oronasal fistula (ONF) is a small hole in the upper jaw bone (maxilla) that creates an abnormal communication path between the oral cavity and the nasal cavity and allows food, saliva and water to enter the respiratory tract, leading to chronic rhinitis (irritation to the nose), sinus inflammation and aspiration pneumonia.
Oronasal fistulas can be congenital (present at birth) or acquired.
- Advanced periodontal (gum) disease which most often affects the upper canine or premolars
- Surgical extraction of a tooth
- Trauma ( vehicular trauma, upper jaw (maxillary) fractures, veterinary (iatrogenic) damage from dental extractions)
- Osteomyelitis (bone infection)
- Bite wounds
- Foreign body penetration
Congenital oronasal fistulas occur during the embryonic stage of development when the palatine shelves fail to fuse, which leaves an opening or cleft. There is a higher incidence in Siamese cats.
- Maternal exposure to toxins during embryonic development
- Genetic inheritance
- Cortisone hormone
- Nutritional (excess vitamin A during pregnancy)
- Viral infections
- Poor maternal nutrition during pregnancy
Most symptoms relate to the passage of water and food from the mouth and can include the following:
- Chronic sneezing
- Pawing at the face
- Blood tinged saliva
- Chronic rhinitis (inflammation of the lining of the nose)
- Mucopurulent or serohemorrhagic nasal discharge on the same side as the fistula
- Difficulty feeding (nursing kittens)
- Milky bubbles come out of the nose when a kitten nurses
- Aspiration pneumonia
It is not always easy for pet owners to spot an oronasal fistula that can be hidden behind existing teeth. It is not uncommon for a cat with chronic rhinitis to be prescribed antibiotics, which clear the condition until the treatment ends and symptoms return.
The veterinarian will perform a physical examination of the cat and obtain a medical history from you, including symptoms and recent dental extractions or traumas.
Proper diagnosis requires a thorough dental examination which will require sedation or general anesthesia to enable the veterinarian to use a periodontal probe. If the veterinarian finds a hole, he will squirt saline solution into it, which will come out through the nose.
- Dental x-rays.
- Pre-anesthetic bloodwork includes a complete blood count and a biochemical profile to evaluate the cat’s overall health, which is necessary for cats undergoing surgery.
Oronasal fistulas cannot heal on their own; the only treatment option is surgical repair. Cats with advanced gum disease may require dental extractions before surgery.
Surgical closure of the fistula involves making a single or double mucogingival flap from the inside lining of the mouth (mucosa), and placing this tissue over the fistula, followed by absorbable stitches to hold it in place until the grafted material heals.
If the oronasal fistula is too large or if surgery fails, an acrylic prosthetic (palatal obturator) may be necessary to plug the hole and prevent food and debris from entering the nasal cavity.
In some cases, the cat will be referred to a specialist dental veterinarian, particularly for difficult or complicated cases.
The cat will be discharged with a care sheet, painkillers, antibiotics and an Elizabethan collar to prevent the cat from damaging the area.
Keep the cat indoors during the recovery period and avoid chews and toys which could damage the repair.
Feed a soft diet until the cat has fully healed.
A follow-up visit will be necessary 1-2 weeks post-surgery to check the cat’s progress.
Diligent dental control as well as an annual scale and clean to prevent gum disease.
Seek immediate veterinary attention if your cat is involved in any trauma, even if the cat appears to be uninjured.