Imaging Guidelines for Facial Cellulitis

Introduction to Imaging Modalities

The American College of Radiology recommends CT orbits with IV contrast as the primary imaging modality for suspected orbital or facial infection, as it differentiates preseptal cellulitis from postseptal cellulitis, identifies abscess formation, detects underlying sinusitis, and evaluates for complications including superior ophthalmic vein thrombosis, cavernous sinus thrombosis, or subdural empyema 1
CT orbits with IV contrast is the most useful imaging modality for evaluating hardware complications, fracture nonunion, and developing osteolysis in patients with a history of trauma or surgery 2, 3, 6

Imaging is essential in specific scenarios, including suspected postseptal involvement, history of trauma or surgery, failure to respond to appropriate antibiotics, and severe systemic symptoms 1, 2, 3, 4
The American College of Radiology suggests that plain X-rays should not be used to rule out necrotizing infection and have minimal role in facial cellulitis evaluation, except in cases of suspected retained foreign body or odontogenic source 2, 3, 4

MRI orbits and head with and without IV contrast is complementary to CT and should be considered when more detailed assessment of intraorbital infection spread is needed, clinical or CT-based suspicion for intracranial complications exists, or evaluation of soft tissue extent, areas of necrosis, or fascial involvement is required 1, 2
Ultrasound has a limited but specific role in differentiating simple cellulitis from necrotizing fasciitis in unstable patients, detecting superficial fluid collections or abscesses, and evaluating soft tissue extent in young children 2, 3, 4

Red flags requiring immediate imaging include pain out of proportion to physical findings, rapidly progressive infection, vision changes, or ophthalmoplegia, which suggest necrotizing infection or postseptal involvement 1, 4
Common pitfalls to avoid include over-reliance on plain films, delaying surgical consultation for imaging, ordering CT head instead of CT orbits, and assuming normal imaging excludes infection 1, 4

In patients with a history of trauma or surgery, CT is superior for evaluating hardware complications, and MRI is challenging due to marrow signal heterogeneity from prior trauma 2, 3, 6
In pediatric patients, CT orbits with IV contrast remains the primary imaging modality, and ultrasound is more valuable due to larger cartilage-to-bone ratio and small body size 1, 3