An oronasal fistula is an abnormal open path from the oral cavity into the nasal sinus. In most cases it is not visible as a hole in the roof of the mouth; the fistula usually is along the root of a tooth.
The most common teeth affected is the upper canine tooth (the large front corner teeth). the second most common teeth affected are the large upper fourth premolars. The problem can occur adjacent to any tooth in the upper jaw. Oronasal fistula can also occur in the center of the hard palate.
Any dog breed can be affected, but dachsunds are by far the most common breed in which we encounter oronasal fistula. They are also more common in toy breeds, and they are rare in cats.
Oronasal fistulas are holes in the bone of the upper jaw. These holes are usually the result of chronic periodontal disease. As periodontal disease progresses bone is lost from the socket of the tooth, and eventually this bone loss extends into the nasal passage. Other causes of oronasal fistula that we have encountered include:
~ Trauma to teeth or palate
~ A foreign object, eg, a stick, bone or other object the pet was chewing, penetrating the space along a root
~ Oral tumors extending into the nasal passage
~ Malocclusion that places the crown of a lower tooth against the upper jaw
~ Congenital defect
Occasionally an oronasal fistula is visible on the oral exam of an awake patient. Usually we need to do an anesthetized oral exam to make the diagnosis. Dental x-rays, and sometimes skull x-rays,are needed to assess the extent of the problem.
When an oronasal fistula occurs alongside a tooth or teeth, the tooth or teeth must be extracted.
If there is a foreign object or oral tumor present we will remove it. This procedure ranges from simple to very complicated. Some oral tumors are inoperable.
Once the tooth, foreign object, or tumor is removed we create a flap of healthy mucosa (the soft tissue lining the oral cavity) adjacent to the fistula. We slide the flap over the fistula and suture it in place.
Healing following oronasal fistula repair usually occurs without complication. In a small but significant number of cases, however, the flap that was sutured in place fails and the fistula re-opens.
Failure of a properly placed flap is due to the constant tension on the margins of the flap caused by the pet breathing in and out through its nose.
In some cases we will surgically replace the failed flap, and in some cases we will allow the fistula to heal by second intention (contracting closed and filling in with healthy scar tissue). Healing by second intention can take weeks to months, but it is not a painful process and does not affect the pet's quality of life. Some oronasal fistulas ultimately do not close completely, but a persistently open fistula also is not painful and does not negatively affect the pet's oral or overall health.
In other words, the significant problem is not the fistula itself, but the problem that caused the fistula. Our primary goal is to treat the problem that caused the fistula. The prognosis for the pet's oral and over-all health thus depends on our ability to treat this problem:
~ When the oronasal fistula is due to periodontal disease, a foreign object, trauma, or malocclusion the prognosis is very good to excellent.
~ When the oronasal fistula is caused by an oral tumor or is a congenital defect the prognosis is variable.