What is the best imaging modality for diagnosing sinusitis in the emergency department (ED)?

Best Imaging Modality for Diagnosing Sinusitis in the Emergency Department

CT scan without contrast is the gold standard imaging modality for diagnosing sinusitis in the emergency department when imaging is clinically indicated. 1

When Imaging Is NOT Indicated

• Uncomplicated acute sinusitis should be diagnosed based on clinical criteria alone without any radiographic imaging 1
• Imaging should not be obtained to distinguish bacterial from viral sinusitis in uncomplicated cases 1

When Imaging IS Indicated

Imaging should be considered in the following scenarios:

• Persistent sinusitis (worsening course or severe presentation not responding to treatment) 1
• Recurrent or chronic sinusitis 1
• When complications are suspected:
  • Orbital complications (proptosis, orbital pain, vision changes) 1
  • Intracranial complications (altered consciousness, seizures, focal neurological deficits) 1
  • Soft tissue involvement 1

Imaging Modality Selection

CT Scan (First-Line When Imaging Is Indicated)

• Non-contrast CT is the gold standard for evaluating sinusitis 1, 2
• Benefits:
  • Accurately depicts sinus anatomy and soft-tissue changes 1
  • Shows potential anatomic variants that may predispose to sinusitis 1
  • Provides essential anatomical detail for surgical planning 1
  • Low-dose protocols available with radiation dose similar to two radiographic views 1
  • Multidetector CT allows for volume isometric imaging with reconstructions in multiple planes 1

CT with IV Contrast

• Reserved for cases with suspected complications 1
• Should include coverage of sinuses, orbits, and brain when complications are suspected 1
• Benefit: Shorter scan time compared to MRI, reducing need for sedation in children 1

MRI

• Not first-line for sinusitis in the ED 1
• Indications for MRI:
  • Suspected intracranial complications (more sensitive than CT - 93% vs 63%) 1, 3
  • Suspected fungal sinusitis 1
  • Suspected neoplasm 2
• Limitations:
  • Does not demonstrate bony detail of the osteomeatal complex well 1
  • Less sensitive to bony erosions 1
  • May require sedation in young children or uncooperative patients 1
  • Longer scan time than CT 1

Plain Radiography

• Limited role in sinusitis evaluation in the ED 1, 2
• Significant limitations:
  • Low sensitivity (57-67%) and variable specificity compared to CT 4
  • Poor visualization of ethmoid and sphenoid sinuses 1
  • High false-negative (32%) and false-positive (49.2%) rates 1
  • Cannot adequately visualize the osteomeatal complex 5
  • Difficult to perform properly in some patients 1

Special Considerations

Nosocomial Sinusitis in ICU Patients

• High index of suspicion needed in ICU patients with unexplained fever 6
• Risk factors include nasotracheal tubes and nasogastric tubes 6
• CT is the preferred imaging modality for diagnosis 6

Immunocompromised Patients

• Lower threshold for imaging due to risk of invasive fungal sinusitis 1
• CT with contrast should be considered to evaluate for invasive disease 1
• MRI may be needed to assess early changes of fungal sinusitis 1

Common Pitfalls to Avoid

• Relying on imaging alone for diagnosis - clinical correlation is essential 1
• Overdiagnosis based on incidental CT findings - mucosal thickening can be seen in up to 40% of asymptomatic adults 2
• Delaying treatment while waiting for imaging in cases of suspected complications 7
• Using plain radiographs for complex cases or surgical planning 1, 4, 5