D. Perform an emergency orbital exploration with lesion biopsy
The differential diagnosis of acute proptosis in an adolescent includes orbital cellulitis, abscess, orbital vascular lesion with or without intralesional hemorrhage, spontaneous orbital hematoma, traumatic carotid-cavernous fistula, orbital inflammatory syndrome, rhabdomyosarcoma, metastatic neuroblastoma, ruptured dermoid cyst, Ewing sarcoma, and leukemia-associated myeloid sarcoma.
There was no inflammation on the MRI scan to support orbital cellulitis, which would be treated by intravenous antibiotics (choice A), or orbital inflammatory syndrome, which would be treated by high-dose steroids (choice C). The patient did not have periorbital ecchymosis, which is often seen in metastatic neuroblastoma. Because 90% of neuroblastomas present in children younger than 5 years, screening for neuroblastoma via urine homovanillic and vanillylmandelic acid testing would be low yield in a 16-year-old patient (choice B). Urgent exploratory surgery (choice D) was indicated given the potential for visual compromise in the setting of decreased visual acuity, high intraocular pressures, optic disc edema, and choroidal folds.