Orbital masses, including tumors and abscesses, can be difficult to detect with traditional radiography. Orbital ultrasonography can depict masses and differentiate fluid from solid tissue, while CT and MRI can further define the extent of a mass within the orbit and adjacent structures. CT is most helpful for delineating bony destruction associated with an orbital mass.
Ultrasonography (performed with the probe placed on the cornea or via a temporal approach) is often recommended as an initial screening procedure, with CT or MRI recommended according to the results of ultrasonography. Although these imaging techniques are very useful, the cause of an orbital mass can be definitively diagnosed only by performing a biopsy or aspiration of affected tissues. The following images were obtained from a dog with an orbital spindle cell sarcoma diagnosed by biopsy.