Computed tomography and ultrasound in the evaluation of orbital infection and pseudotumor.

Twenty patients with orbital inflammatory processes were examined with high-resolution computed tomography (CT) and 14 of them were also evaluated with ultrasound (US). In eight cases of orbital infection, six abscesses were localized by CT; US contributed no significant additional information. The 12 cases of orbital pseudotumor could be classified into four forms by CT. US added specificity to the CT findings, especially in the tumefactive form. In all eight cases of pseudotumor where US was performed, low-reflective echoes were characteristically seen. In addition, edema in the retrobulbar fascia (four cases) was continuous with fluid along the optic nerve sheath (three cases) and muscle enlargement was identified in six cases. These US features were found to be important in the differential diagnosis of intra-orbital masses.