What is the best X-ray (radiograph) view for a patient with facial cellulitis, particularly those with a history of trauma or surgery?

Best X-ray for Facial Cellulitis

Plain radiographs (X-rays) are NOT the appropriate initial imaging for uncomplicated facial cellulitis—CT orbits with IV contrast is the imaging modality of choice when imaging is clinically indicated, particularly when there is concern for postseptal involvement, abscess formation, or underlying sinusitis. 1

When Imaging is Actually Needed

Most cases of facial cellulitis are diagnosed clinically and do not require imaging at all. However, imaging becomes essential in specific scenarios:

• Suspected postseptal (orbital) involvement: Look for proptosis, limitation of extraocular movements, or vision changes—these indicate infection posterior to the orbital septum and mandate imaging 1
• History of trauma or surgery: When there is concern for underlying osteomyelitis, hardware infection, or retained foreign body 1
• Failure to respond to appropriate antibiotics: Consider imaging to evaluate for abscess, deeper infection, or alternative diagnosis 1
• Severe systemic symptoms: Fever, tachycardia, or signs suggesting necrotizing infection 1

Imaging Algorithm for Facial Cellulitis

First-Line Imaging: CT Orbits with IV Contrast

CT of the orbits with IV contrast is the most useful imaging modality for suspected orbital or facial infection. 1 This study:

• Differentiates preseptal cellulitis (anterior to orbital septum) from postseptal cellulitis (posterior to orbital septum) 1
• Identifies abscess formation requiring drainage 1
• Detects underlying sinusitis (particularly ethmoid sinusitis, the most common source) 1
• Evaluates for complications including superior ophthalmic vein thrombosis, cavernous sinus thrombosis, or subdural empyema 1

Important caveat: Precontrast imaging is typically not necessary and adds unnecessary radiation without diagnostic benefit 1

When Plain Radiographs Have Limited Utility

Plain X-rays should not be used to rule out necrotizing infection and have minimal role in facial cellulitis evaluation 1. The only scenarios where plain films might be considered:

• Suspected retained foreign body: Plain radiographs can detect radiodense foreign bodies (metal, stone, graphite, some glass) 1
• Odontogenic source: Dental radiographs may identify dental caries or mandibular pathology as the infection source 2

However, even for foreign bodies, CT without IV contrast is 5-15 times more sensitive than radiography and should be the preferred modality 1

Advanced Imaging Considerations

MRI orbits and head with and without IV contrast is complementary to CT and should be considered when: 1

• More detailed assessment of intraorbital infection spread is needed
• Clinical or CT-based suspicion for intracranial complications exists
• Evaluation of soft tissue extent, areas of necrosis, or fascial involvement is required 1

Ultrasound has a limited but specific role: 1

• Can differentiate simple cellulitis from necrotizing fasciitis in unstable patients who cannot undergo CT 1
• Useful for detecting superficial fluid collections or abscesses 1
• Limited by inability to visualize deeper structures and hindrance by bone and gas 1

Critical Clinical Pearls

Red Flags Requiring Immediate Imaging

• Pain out of proportion to physical findings: Suggests necrotizing infection—imaging should not delay surgical consultation 1
• Rapidly progressive infection: Treat as necrotizing infection from the beginning; clinical picture may worsen within hours 1
• Vision changes or ophthalmoplegia: Indicates postseptal involvement with risk of vision loss from retinal artery occlusion or optic nerve injury 1

Common Pitfalls to Avoid

• Over-reliance on plain films: They are insensitive for soft tissue infections and miss most complications 1
• Delaying surgical consultation for imaging: In unstable patients or those with suspected necrotizing infection, imaging should never delay operative intervention 1
• Ordering CT head instead of CT orbits: CT head does not provide adequate orbital detail for facial cellulitis evaluation 1
• Assuming normal imaging excludes infection: Early necrotizing infections may not show characteristic findings like subcutaneous gas on plain films 1

Special Populations

Patients with history of trauma or surgery: 1

• CT is superior for evaluating hardware complications, fracture nonunion, and developing osteolysis
• MRI is challenging in chronic post-traumatic settings due to marrow signal heterogeneity from prior trauma
• Consider both osteomyelitis and hardware infection in the differential

Pediatric patients: 1

• CT orbits with IV contrast remains the primary imaging modality
• Risk factors for postseptal inflammation include age >3 years, high neutrophil count, absence of infectious conjunctivitis, and gross periorbital edema
• Ultrasound is more valuable in young children due to larger cartilage-to-bone ratio and small body size