Differential diagnoses for bilateral ocular and orbital disease in this case included infectious causes such as systemic fungal
disease (cryptococcosis, aspergillosis, blastomycosis, penicilliosis, histoplasmosis)1-9 or aerobic or anaerobic bacteria,10,11 neoplastic processes (lymphosarcoma, squamous cell carcinoma, osteoma, osteosarcoma, fibrosarcoma),10,12,13 and primary inflammatory disorders (eosinophilic, pseudotumor).11,14,15
Because of the patient's fractious nature, the cat was placed under general anesthesia and intubated to allow maintenance
of anesthesia with isoflurane while a complete blood count (CBC), a serum chemistry profile, thoracic radiography, and orbital
and ocular ultrasonography and aspiration were performed. A temporary tarsorrhaphy of the left eye was also performed to provide
CBC and serum chemistry profile
The only significant abnormalities noted were hyperproteinemia (8.2 g/dl; reference range = 6 to 7.5 g/dl) and a mild mature
neutrophilia (15.4 x 103/µl; reference range = 2.5 to 12.5 x 103/µl), which were both attributed to inflammation.
Thoracic radiography showed a pneumomediastinum with extension into the retroperitoneum, likely induced by barotrauma. Barotrauma
most commonly occurs as a complication of mechanical ventilation and results in extra-alveolar air accumulation.
On follow-up radiography, no pulmonary parenchymal abnormalities were found, the pneumomediastinum had resolved, and thoracic
radiography results were considered normal.
Ocular ultrasonography confirmed a partial retinal detachment in the right eye. A diffusely thickened and completely detached
retina was identified in the left eye (Figure 2).
2. A dorsal oblique plane ultrasonographic image of the left globe showing a diffusely thickened and completely detached retina.
Orbital ultrasonography results showed a homogenous retrobulbar mass, measuring 2.2 x 1.5 cm, deforming the posterior sclera
on the left side (Figure 3). A similar but smaller (1.9 x 0.8 cm) homogenous mass was noted in the right orbit. Fine-needle aspiration of the left retrobulbar
mass was performed for cytologic examination.
3. A dorsal plane ultrasonographic image of the homogenous left retrobulbar mass displacing the sclera.
Moderate numbers of adequately preserved nucleated cells with mild-to-moderate blood contamination were noted (Figure 4). Moderate numbers of small, mature lymphocytes; a few slightly vacuolated macrophages; and a few nondegenerate neutrophils
were present. Low numbers of small (2 or 3 µm long and 1 or 2 µm wide), round-to-oval yeast were present both extracellularly
and phagocytosed by the macrophages. These yeast were surrounded by a thin clear halo and contained a small, eccentrically
located, crescent-shaped purple nucleus.
4. Cytologic examination findings from the fine-needle aspiration of the left retrobulbar mass seen in Figure 3. Note the
macrophage with phagocytosed Histoplasma capsulatum yeast; rare, small, mature lymphocytes; and aggregates of erythrocytes
(Diff-Quik—Dade Behring; bar = 20 µm).
The cytologic interpretation was granulomatous inflammation with intracellular Histoplasma capsulatum organisms.