Suspected Rhinolithiasis Associated With Endodontic Disease in a Cat

Introduction

The differential diagnosis for radiopaque objects within the nasal cavity includes foreign bodies, retained roots, impacted teeth, sequestra, calcified neoplasms, and rhinoliths. Rhinoliths are mineralized masses found in the nasal cavity that form around an intranasal nidus via the precipitation of mineral salts derived from nasal and inflammatory secretions. ^{1 –4} Depending on its origin, a nidus may be classified as exogenous or endogenous. ^{1,2,4 –7} Rhinolithiasis is considered rare in humans and has only recently been reported in 2 dogs. ⁷ Endogenous rhinoliths are reportedly even less common than exogenous rhinoliths ¹ and have not been reported in the veterinary literature. Clinical signs are consistent with inflammatory rhinitis and nasal obstruction. However, asymptomatic cases are not uncommon and rhinoliths may be identified as an incidental finding on diagnostic imaging studies of the skull and oral cavity. ^{4,6,8 –10} This article describes a suspected case of endogenous rhinolithiasis in a cat associated with endodontic disease in a maxillary canine tooth.

Case Report

A 15-year-old female neutered domestic longhair cat was presented for assessment of a fractured left maxillary canine tooth (204). Packed cell volume, total protein, and serum biochemistry profile performed prior to surgery did not reveal any significant changes. The patient was premedicated with methadone ^a (0.4 mg/kg) by intramuscular injection. General anesthesia was induced with intravenous alfaxalone ^b (2.6 mg/kg) followed by endotracheal intubation with a cuffed endotracheal tube. Anesthetic maintenance was achieved with variable rate isoflurane ^c in oxygen. A balanced isotonic electrolyte solution ^d was administered throughout the procedure at 10 mL/kg/h.

An oral examination including periodontal probing was performed. This revealed a complicated crown fracture of tooth 204 with discoloration of the crown. An uncomplicated crown fracture of the right maxillary third incisor tooth (103) was also noted. Due to the geriatric nature of the patient, selective radiographs were performed based on the oral examination to reduce anesthetic time. A bisecting angle radiograph of tooth 204 revealed a periapical lucency with inflammatory root resorption (Figure 1). Upon closer inspection of the radiograph, a radiopaque structure was noted apical to the canine tooth.

OPEN IN VIEWER

Figure 1.

Pre-extraction bisecting angle radiograph of the fractured left maxillary canine tooth. There is a periapical lucency with inflammatory resorption of the root apex (black arrow). A radiopaque structure is visible apical to the left maxillary canine (white arrow).

The patient’s teeth were ultrasonically scaled supragingivally and subgingivally with a water-cooled magnetostrictive ultrasonic scaler ^e and polished with prophylaxis paste and a prophy cup on a low-speed handpiece. Due to the severity of root resorption, the decision was made to surgically extract tooth 204. After extraction, a bisecting angle radiograph was obtained and showed a vacated alveolus (Figure 2). This radiograph showed an irregular, heterogeneous structure of mineral opacity, apical to the alveolus of the canine tooth. Exploration of the canine tooth alveolus with a periodontal probe ^f revealed an oronasal communication. The probe was passed into the nasal cavity via the alveolus, where it came into contact with a hard, mobile object. An occlusal radiographic view was obtained to help further evaluate the location of the object (Figure 2).

OPEN IN VIEWER

Figure 2.

Postoperative bisecting angle (A) and occlusal (B) views of the left maxillary canine tooth alveolus. There is a heterogeneous, radiopaque structure with an irregular, well-defined border in the left nasal cavity (white arrows).

A transalveolar approach to the nasal cavity was performed to remove the intranasal object. The existing pedicle mucogingival flap created to extract the canine tooth was extended apically. The existing communication between the oral and nasal cavities was expanded with a size 4 carbide round cutting bur. This facilitated passage of a Miller surgical curette ^g into the nasal cavity, which was then used to gently extract the object in 2 pieces, along with a small amount of purulent material. An occlusal radiograph of the maxilla was obtained to confirm complete removal of the object (Figure 3). Alveoloplasty was performed with a round cutting bur prior to tension-free apposition of the mucogingival flap using 5-0 poliglecaprone 25 suture ^h in a simple interrupted pattern. Postoperative analgesia consisted of transmucosal buprenorphine ⁱ (0.01 mg/kg every 12 hours) for 5 days. Due to concerns regarding poor patient cooperation and medication compliance, postoperative antibiotic coverage with a single subcutaneous injection of cefovecin ^j (5.5 mg/kg) was administered. The client was counselled about the possibility of lip entrapment secondary to the removal of tooth 204.

OPEN IN VIEWER

Figure 3.

Postoperative occlusal view of the maxilla confirming complete removal of the radiopaque nasal object.

Examination of the removed intranasal lesion revealed a 5-mm diameter, irregular, tan, hard, friable object that resembled dental calculus in appearance and consistency (Figure 4). There was no evidence of a grossly identifiable nidus when the object was sectioned. Further diagnostic testing on the removed object was declined.

OPEN IN VIEWER

Figure 4.

The suspected rhinolith removed from the nasal cavity of a cat.

Reexaminations at 3 and 14 days postoperatively revealed satisfactory healing of the surgery sites and the client reported no clinical signs of nasal disease. Further follow-up was conducted by phone 18 months postoperatively. The client reported that the patient continued to be doing well and had not developed any clinical signs of nasal disease.

Rhinolithiasis was considered the most likely diagnosis in this case based on the radiographic and gross appearance of the intranasal object, its location free within the nasal cavity, its association with a maxillary canine tooth affected by endodontic disease, and the lack of progression to clinical nasal disease after the object’s removal.

Discussion

The first report of a rhinolith is commonly attributed to Bartholin in 1654. ¹ They are rare, with only 28 cases reported in the human literature over a 17-year period between 1988 and 2005. ⁶ In comparison, there have only been 2 reported cases of rhinolithiasis in companion animals, both in dogs. ⁷ Rhinoliths are almost always unilateral and are typically located in the ventral aspect of the nasal cavity about midway between the anterior and posterior nares in humans. ¹ However, bilateral rhinolithiasis has been reported, ^1,8 as have rhinoliths in the nasopharynx, and in more dorsal locations within nasal cavity. ¹ Similar concretions have also been reported in the maxillary, frontal, sphenoid, and ethmoid sinuses in people. ¹ Such concretions are known as antroliths when they occur within the maxillary sinus. ¹¹ The gross appearance of rhinoliths can be variable. ¹ In humans, they are usually irregular in shape, and of varying shades of brown, occasionally with green or black hues. ¹ There are also a few reports of stones having an annular or laminated appearance when sectioned. ^1,9 Consistency of rhinoliths varies from hard to friable or chalky. ¹

Although the exact process by which rhinoliths are formed is uncertain, ^3,6,12 it is commonly accepted that they form and grow through precipitation of mineral salts around an exogenous or endogenous nidus. ^2,5,6,8 The mineral salts are derived from chronic inflammatory secretions associated with the offending nidus, ^6,7 although normal nasal and lacrimal secretions may also be involved. ^2,10 Deposition of mineral salts reportedly occurs despite normal serum calcium and phosphate levels. ¹¹ Mechanical obstructions preventing the outflow of secretions, ^6,12 and alterations in nasal airflow, ^3,9,12 are also believed to contribute to the precipitation of mineral salts. This hypothesis may explain why the 2 cases reported in dogs to date have occurred in small, brachycephalic breeds. ⁷ The amount of time required for a rhinolith to form is unclear. ³ In Polson’s review of 384 human cases prior to 1943, patients were most commonly diagnosed with rhinolithiasis in their second and third decades of life, while the time of foreign body insertion was most common during the first decade of life, ¹ indicating that the process of encrustation is likely to take years.

Exogenous nidi include fruits, seeds, beads, and pebbles, among others. ^3,4,6,9 The most common route of entry is the nares, ¹ although retrograde entry via the nasopharynx ^1,6 and iatrogenic insertion ¹² is possible. In humans, they are frequently inserted into the nares by the patient during childhood and forgotten. ^4,5,8,9 The lesser likelihood of companion animal species intentionally introducing foreign objects into the nasal cavity, the length of time required for encrustation to occur, and the shorter life span of cats and dogs in comparison to humans, may explain why so few cases of rhinolithiasis have been reported in veterinary patients to date. Endogenous nidi include teeth, sequestra, dried pus, dried blood clots, nasal secretions, and cellular debris. ^2,4,10 They are reported to be much less common, with Polson reporting a ratio of exogenous to endogenous nidi of 7:1. ¹ Plant material has been previously identified as a nidus in a dog. ⁷ Associations between odontogenic disease and nasal disease have previously been established in companion animals. ^13,14 A recent evaluation of dogs with lymphoplasmacytic rhinitis found an association with odontogenic infection in 55% of cases. ¹⁴ The intranasal object in the present case was closely associated with a fractured maxillary canine tooth with pulp exposure. There was radiographic evidence of a periapical lucency and inflammatory root resorption, indicating endodontic disease. The nasal cavity and the apex of the maxillary canine teeth have a close anatomical relationship in cats (Figure 5). Therefore, significant odontogenic disease is likely to extend into the nasal cavity in this region. Potential mechanisms by which the affected tooth could have contributed a nidus include root fracture, root fragmentation associated with tooth resorption, sequestration of the nasal bone plate, or cellular debris associated with necrosis or chronic inflammation. While a nidus could not be identified on gross examination, this does not rule out a diagnosis of rhinolithiasis, as not all rhinoliths have a readily identifiable nidus. ^1,2 Potential explanations for the lack of an identifiable nidus include a small nidus requiring microscopy for identification, degradation of the nidus by an inflammatory process, or expulsion of the nidus prior to diagnosis.

OPEN IN VIEWER

Figure 5.

Transverse computed tomography slice of a normal feline head study at the level of the maxillary canine apices. Note the close anatomical relationship between the lumen of the nasal cavity and the apices of the maxillary canine teeth (black stars). Image courtesy of the Veterinary Imaging Centre.

While the patient in this case did not display any clinical signs of nasal disease, previously reported clinical signs of rhinolithiasis in humans include nasal obstruction, foul-smelling nasal discharge, epistaxis, facial swelling, epiphora, pyrexia, and pain. ^1,6,8,9 Schuenemann and Oechtering described 2 cases in dogs where rhinoliths presented with chronic nasal obstruction and discharge, resulting in severe dyspnea. ⁷ However, the presence and duration of clinical signs do not necessarily correlate with the duration or size of the rhinolith, ⁸ and cases may be asymptomatic at the time of diagnosis. ^4,6,8,9 In human cases where the rhinolith has been present for an extended duration, complications such as erosion or deviation of the nasal or maxillary septum, palatal perforation, oronasal fistulae, destruction of the nasal mucosa, formation of sequestra, and sinusitis have been reported. ^2,5,6,8,10 Nasal septum deviation has also been reported in companion animals. ⁷ While in the case reported here there was no evidence of nasal septum deviation or palatal perforation, it is possible that computed tomographic (CT) evaluation may have identified complications not visible on radiographs.

Rhinoscopy, ¹² intraoral radiography, ^6,8 and CT imaging ⁴ have been used alone or in combination for the diagnosis of rhinolithiasis in humans. As many human cases are asymptomatic, dentists have frequently been the first to diagnose the condition during intraoral or panoramic radiographic projections. ^6,8,9 Similarly, in the case described above, the suspected rhinolith was an incidental finding on periapical radiographs obtained for assessment of a fractured left maxillary canine tooth.

Computed tomographic evaluation is the preferred imaging modality due to the production of cross-sectional scans that aid in the determination of the exact location, size and shape of rhinoliths, ¹⁰ its higher sensitivity for detecting small amounts of calcium, ⁶ and the lack of superimposition of anatomic structures. ⁹ Computed tomographic imaging may also provide further information on complications such as sinusitis, septal deviation, or palatal perforation. ^2,5,10 If 2-dimensional imaging techniques are used alone, several views are required to evaluate the shape, size, and location of the rhinolith. ⁹

Macintyre is credited as the first author to describe the radiographic appearance of a rhinolith in 1900. ¹ They appear as homogeneous or heterogeneous radiopacities in the nasal cavity of variable shape and size. ¹¹ The border of the lesion is typically radiopaque with a corrugated outline, ⁸ although this can vary. ¹¹ Areas of central lucency, correlating with more radiolucent nidi, ⁸ and annular radiographic characteristics, ¹¹ have also been reported in people. The differential diagnosis for radiopaque objects within the nasal cavity includes radiopaque foreign bodies, retained roots, impacted teeth, and sequestra. ⁹ Calcified neoplasms such as calcified nasal polyps, ossifying fibromas, osteomas, chondromas, osteosarcomas, chondrosarcomas, and odontomas should also be considered. ⁹ While a detailed discussion comparing the radiographic appearance of radiopaque lesions of the nasal cavity is outside the scope of this report, it can be said that some possible causes may be more easily differentiated from rhinoliths than others. For example, osteosarcomas typically have a poorly defined margin and are associated with loss of trabecular structure of the affected bone, while chondrosarcomas frequently have a flocculent central radiopaque structure. ¹⁵ Odontomas have a well-defined periphery but usually have a radiolucent soft tissue capsule immediately inside and adjacent to their corticated border. ¹⁶

In humans, rhinoliths are typically removed transnasally, with endoscopic assistance if necessary. ^2,3,9,12 Irrigation and suction may assist in the removal of smaller rhinoliths, ⁶ while larger concretions can be broken into smaller pieces and removed in a piecemeal fashion ^4,10,12 or displaced into the nasopharynx and removed orally. ⁵ Ultrasound lithotripsy has been used to fragment a rhinolith prior to removal, but this is not considered the treatment of choice. ¹² If the rhinolith cannot be removed by minimally invasive means, or if complications such as palatal perforation are present, a surgical approach to the nasal cavity may be necessary. ^2,5,10 Hemorrhage is a potential complication in these cases. ^5,10 Methods previously used to remove rhinoliths in companion animals include endoscopic removal and laser-assisted turbinectomy, with turbinectomy required in the latter case due to complications associated with chronic rhinitis and previous surgical attempts. ⁷ In the case described above, the suspected rhinolith was easily accessible through the extraction site and did not require an invasive procedure to retrieve it. Although the technique described was successful in removing the offending object in this case, it was only possible with removal of the maxillary canine tooth, and so its wider application is limited for this reason. Potential complications arising from this technique include excessive hemorrhage, and flap dehiscence resulting in a persistent oronasal fistula, neither of which occurred in this case. Other approaches to the nasal cavity include dorsal, ventral, and lateral approaches. ¹⁷ An alveolar mucosal approach to the nasal cavity to remove a foreign body has also been described in dogs. ¹⁸ Recurrence of a rhinolith after removal has not been reported. ³

Multiple reports in the human literature describe rhinolithiasis based on imaging and/or rhinoscopic findings alone. ^5,10,19 However, it is the authors’ opinion that histopathology and mineralogic analysis are essential for definitive diagnosis to confirm the presence of calcium salts and to rule out other disease processes such as neoplasia. Histopathology has also been reported to assist in identification of a small nidus. ⁷ Neoplastic involvement was considered unlikely in this case due to the minimal radiographic changes surrounding the intranasal object and the ongoing absence of clinical signs following removal of the object. Rhinoliths typically consist of approximately 90% inorganic to 10% organic material, with the organic material being derived from nasal secretions. ¹² The main constituent of the inorganic component is calcium phosphate, with lesser amounts of magnesium phosphate and calcium carbonate. ^1,8 Magnesium carbonate, calcium stearate, oxalate, fluoride, chloride, iron, zinc, sodium, and potassium have also been reported in small amounts. ^1,6,8,12 A rhinolith composed completely of calcium carbonate has been reported in a dog. ⁷

Conclusion

Rhinolithiasis is a rare condition that may present as nasal obstruction and discharge in cats and dogs, or as incidental findings on imaging studies of the head and oral cavity in asymptomatic cases. As the use of intraoral radiography becomes more prevalent in veterinary medicine, it is possible that clinicians may be presented with rhinolithiasis as an incidental finding, and it is important to be familiar with the radiographic appearance, differential diagnoses, and treatment options. Stone analysis and/or histopathology are recommended for confirmation of the diagnosis.