Page 145 - Feline diagnostic imaging

144 8 Diseases of the Eye

(b)

(a)

(c)

Figure 8.18 Three-dimensional reconstructed CT image of the skull of a cat with nasal B-cell lymphoma. (a) View from the side.
(b) View obliquely from rostrally and laterally. (c) View from the medial aspect of the skull which has been halved. The nasal
lymphoma represented in red invades into the retroorbital space as well as through the hard palate. Clinically there was associated
bilateral nasal discharge, increased respiratory effort, and mild exophthalmos. Source: Courtesy of Dr Adrien Hespel.

are usually nonspecific for the tissue of origin and etiology
[9]. On ultrasonographic exam, cellulitis can appear as a
diffuse, nondeforming lesion of the retrobulbar space, the
echogenicity of which can vary from diffusely hyperechoic
to subtle hypoechoic areas with a decreased definition of
the normal retrobulbar structure [4,36]. Thus, it is conveni-
ent to perform an ultrasonographic examination of the
contralateral unaffected eye to establish a normal reference
[36]. Retrobulbar abscess appears as a cyst‐like well‐cir-
cumscribed hypoechoic mass with or without deformity of
the posterior wall. Normally, a well‐defined echogenic wall
is appreciated [4,36].
Reported CT signs of orbital inflammation include ros-
tral displacement of the globe, swelling of orbital tissues
and loss of the normal attenuation of the retrobulbar fat,
Figure 8.19 Orbital lymphoma. CT image. There is a large
increase in soft tissue with areas of contrast enhancement which reduces the image contrast, thus obscuring visuali-
associated with the right side of the calvarium. The globe is zation of the extraocular muscles, optic nerve, and globe
displaced rostrally and dorsolaterally due to increased [8,80,81]. Fat stranding has been significantly associated
soft tissue within the caudal aspect of the orbit. The abnormal with inflammatory conditions while delineation of the
tissue extended caudoventrally ventral to the left
tympanic bulla. margin of the lesion was shown to be an important