What Is Your Diagnosis?

Judilee C. Marrow Veterinary Medical Teaching Hospital, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Jennifer L. Johnson-Neitman Veterinary Medical Teaching Hospital, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Gary D. West Veterinary Medical Teaching Hospital, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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History

A 5-year-old spayed female Dutch rabbit was referred for evaluation of exophthalmia of the left eye of 1.5 months' duration. On physical examination, the rabbit weighed 2.64 kg (5.8 lb) and body temperature, respiratory rate, and heart rate were all within reference limits. The left eye was notably exophthalmic and could not be retropulsed with gentle pressure. Ophthalmic examination revealed a miotic left pupil with a positive dazzle reflex; the right eye appeared normal on ophthalmic examination. Palpation of the head and neck and oral examination revealed no clinically relevant abnormalities. Results of hematologic evaluation (from the referring veterinarian) revealed a high percentage of heterophils (62%; reference range, 35% to 55%), although the absolute heterophil count (0.523 × 103 cells/μL; reference range, 0.228 × 103 cells/μL to 0.975 × 103 cells/μL) and WBC count (7.8 × 103 WBCs/μL; reference range, 4 × 103 WBCs/μL to 10 × 103 WBCs/μL) were not high. Serum biochemical analysis did not reveal any clinically important abnormalities. Skull radiographs obtained from the referring veterinarian were evaluated (Figure 1).

Figure 1—
Figure 1—

Lateral (A) and ventrodorsal (B) radiographic views of the skull of a 5-year-old spayed female Dutch rabbit evaluated because of exophthalmia of the left eye of 1.5 months' duration.

Citation: Journal of the American Veterinary Medical Association 238, 4; 10.2460/javma.238.4.427

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page

Diagnostic Imaging Findings and Interpretation

A large soft tissue opacity extending dorsally to the frontal bones and causing an increased opacity of the rostral calvarium and ethmoidal region is evident. There is also increased radiolucency surrounding the superimposed third mandibular molar. The left zygomatic arch is decreased in thickness, compared with the right, with an irregular cortical margination (Figure 2). A poorly defined linear osseous structure seen superimposed on the medial aspect of the left orbit is evident.

Figure 2—
Figure 2—

Same radiographic image as in Figure 1. Notice the soft tissue mass associated with the left orbit (white arrow) and zygomatic arch. There is also a linear osseous structure superimposed on the medial aspect of the left orbit (asterisk).

Citation: Journal of the American Veterinary Medical Association 238, 4; 10.2460/javma.238.4.427

Computed tomography of the skull was performed by use of a helical scanner (Figure 3). A large multilobular peripherally contrast-enhancing soft tissue density mass, measuring approximately 2.2 × 2.1 × 3.3 cm, is seen medial to the left zygomatic arch. The soft tissue density mass is causing dorsolateral displacement of the left retrobulbar fat and globe and extends ventral to the level of the left mandibular cheek teeth. The left zygomatic arch is decreased in thickness, compared with that of the right, and there is widening of the mandible in the region of the left mandibular second and third molars. The left third mandibular molar is overgrown, curving laterally into the buccal soft tissues.

Figure 3—
Figure 3—

Computed tomographic images of the skull of the same rabbit as in Figure 1. A—Postcontrast transverse image (slice thickness, 1 mm) at the level of third mandibular molar. Notice the contrast-enhancing soft tissue density mass (asterisk) causing exophthalmia of the left eye, a decrease in the width of the left zygomatic arch (arrowhead), and an increase in the width of the left mandible (arrow). B—Multiplanar reformatted dorsal plane image at the level of the mandible. Notice the left third mandibular molar overgrowth (arrow).

Citation: Journal of the American Veterinary Medical Association 238, 4; 10.2460/javma.238.4.427

Comments

Cytologic evaluation of a fine-needle aspirate of the mass revealed necrotic debris with granulomatous and heterophilic inflammation, consistent with an abscess. Surgical exploration of the site revealed a large encapsulated abscess that extended dorsally from the level of the left mandibular molars, under the left zygomatic arch, and into the left retrobulbar space. A communication between the abscess and the oral cavity, surrounding the overgrown left third mandibular molar, was identified. En bloc resection of the abscess was performed without enucleation of the left eye.

The most common cause of unilateral exophthalmia in rabbits is retrobulbar abscess formation secondary to endodontic disease.1 Although disease of the maxillary cheek is a more likely cause of exophthalmia, the rabbit of this report was unique in that the abscess originated from the left mandibular molars with extension to involve the zygomatic arch and the floor of the left orbital cavity. Diagnostic imaging of dental disease in rabbits has traditionally involved multiple radiographic views of the skull to visualize the tooth roots. Computed tomography can overcome the superimposition of structures seen in conventional radiographic images; it also can identify areas of osteomyelitis, abscess formation, or bone loss.2

  • 1.

    Wagner FFehr M. Common ophthalmic problems in pet rabbits. J Exot Pet Med 2007; 16: 158167.

  • 2.

    Capello VCauduro A. Clinical technique: application of computed tomography for diagnosis of dental disease in the rabbit, guinea pig, and chinchilla. J Exot Pet Med 2008; 17: 93101.

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  • Figure 1—

    Lateral (A) and ventrodorsal (B) radiographic views of the skull of a 5-year-old spayed female Dutch rabbit evaluated because of exophthalmia of the left eye of 1.5 months' duration.

  • Figure 2—

    Same radiographic image as in Figure 1. Notice the soft tissue mass associated with the left orbit (white arrow) and zygomatic arch. There is also a linear osseous structure superimposed on the medial aspect of the left orbit (asterisk).

  • Figure 3—

    Computed tomographic images of the skull of the same rabbit as in Figure 1. A—Postcontrast transverse image (slice thickness, 1 mm) at the level of third mandibular molar. Notice the contrast-enhancing soft tissue density mass (asterisk) causing exophthalmia of the left eye, a decrease in the width of the left zygomatic arch (arrowhead), and an increase in the width of the left mandible (arrow). B—Multiplanar reformatted dorsal plane image at the level of the mandible. Notice the left third mandibular molar overgrowth (arrow).

  • 1.

    Wagner FFehr M. Common ophthalmic problems in pet rabbits. J Exot Pet Med 2007; 16: 158167.

  • 2.

    Capello VCauduro A. Clinical technique: application of computed tomography for diagnosis of dental disease in the rabbit, guinea pig, and chinchilla. J Exot Pet Med 2008; 17: 93101.

    • Crossref
    • Search Google Scholar
    • Export Citation

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