What is the best imaging study to diagnose orbital cellulitis?

The best imaging study to diagnose orbital cellulitis is contrast-enhanced CT of the orbits. This imaging modality provides excellent detail of the soft tissues, orbits, and surrounding structures, which is essential for assessing the extent of the infection, possible complications, and differentiating orbital cellulitis from conditions with similar presentations, such as preseptal cellulitis.

Contrast-enhanced CT allows for visualizing both the orbital contents and associated structures, including the ocular muscles, fat, and any potential abscess formation. In contrast, other imaging studies have limitations; for instance, X-rays are not generally useful in evaluating soft tissue infections, as they primarily provide bone detail. Ultrasound can occasionally detect fluid collections but lacks the comprehensive detail needed for definitive diagnosis. MRI, while useful in some cases for characterizing soft tissue pathologies in the orbit, is less commonly used in acute settings due to longer acquisition times and limited availability in emergency situations.

Overall, contrast-enhanced CT remains the gold standard for confirming orbital cellulitis and guiding appropriate management, including surgical intervention if necessary.