A 4-year-old with orbital cellulitis should undergo which diagnostic imaging?

• A. Applanation tonometry
• B. Electronystagmography
• C. Orbital and sinus CT scan
• D. Ultrasonography of sinuses

Answer: (C)

When orbital cellulitis is suspected, imaging is used to define how far the infection has spread, distinguish it from preseptal cellulitis, and look for complications or a sinus source. A contrast-enhanced CT scan of the orbits and paranasal sinuses is the study of choice in a child because it rapidly provides detailed images of the orbital contents, extraocular muscles, optic nerve, and the surrounding sinuses. This helps determine if the infection has extended behind the orbital septum, involves the posterior orbit or apex, or there is a subperiosteal or orbital abscess that may require drainage, all of which guide management decisions like antibiotics versus surgical intervention. While other tests can assess unrelated ocular functions or sinus disease, they don’t give the comprehensive view needed for acute orbital infections. Ultrasonography of the sinuses is less reliable for assessing orbital involvement and potential abscesses, and CT uniquely balances speed, accuracy, and clinical utility in this scenario. MRI can be considered if there’s concern for intracranial extension or if radiation risk is a concern and CT results are inconclusive.