Will a plain sinus X‑ray reliably detect an acute sinus infection?

Will X-ray Show Sinus Infection?

Plain sinus X-rays should not be obtained for diagnosing acute sinus infections because they have poor sensitivity (only 57-76%), cannot reliably visualize the ethmoid sinuses, and cannot distinguish bacterial from viral infection—making clinical diagnosis based on symptoms alone both more accurate and cost-effective. 1

Why X-rays Are Not Recommended

Limited Diagnostic Accuracy

• Plain radiographs have moderate sensitivity (76%) and specificity (79%) compared to maxillary sinus puncture (the gold standard), but this performance is comparable to clinical criteria alone 1
• X-rays miss disease in the ethmoid sinuses entirely—which are involved in approximately 20% of acute sinusitis cases—because the fine bony anatomy cannot be visualized due to structural superimposition 1, 2
• Frontal and sphenoid sinuses are also poorly assessed on plain films 3, 4
• Even when positive, X-rays show air-fluid levels or complete opacification in only 60% of actual sinusitis cases 5

Cannot Distinguish Viral from Bacterial Infection

• Sinus involvement is common in documented viral upper respiratory infections, making it impossible to distinguish acute bacterial rhinosinusitis (ABRS) from viral rhinosinusitis (VRS) based solely on imaging 1
• Mucosal thickening persists for up to 8 weeks after viral infections, so radiographic abnormalities do not correlate with need for antibiotics 1, 2
• The decision to treat with antibiotics must be made on clinical grounds, not imaging findings 1

Official Guideline Position

• The American Academy of Otolaryngology-Head and Neck Surgery explicitly states: "Clinicians should not obtain radiographic imaging for patients presenting with uncomplicated acute rhinosinusitis" 1
• The American College of Radiology has declared that plain films are inaccurate in a high percentage of patients and should be supplanted by CT imaging when imaging is truly needed 1

When Imaging IS Indicated (Use CT, Not X-ray)

If imaging becomes necessary, non-contrast CT is the appropriate modality, not plain X-rays 1, 2, 5:

Absolute Indications for CT Imaging

• Suspected complications: orbital swelling, proptosis, cranial nerve palsies, severe headache, facial swelling, or altered mental status 1, 2
• Immunocompromised patients: diabetes, HIV, transplant recipients (lower threshold due to risk of invasive fungal sinusitis) 1
• Pre-operative planning before endoscopic sinus surgery 1, 2
• Suspected alternative diagnosis: malignancy, Wegener granulomatosis, allergic fungal sinusitis 1, 2
• Recurrent or refractory disease despite optimal medical therapy 1, 2

How to Diagnose Acute Sinusitis Clinically

The diagnosis should be made based on history and physical examination alone 2:

Clinical Criteria for Bacterial Sinusitis

• Purulent nasal discharge (cloudy or colored, not clear) PLUS one or both of: 1, 2
  • Nasal congestion/obstruction
  • Facial pain, pressure, or fullness (especially unilateral over a specific sinus)

Timing Distinguishes Bacterial from Viral

• Viral sinusitis: symptoms present <10 days and not worsening 1
• Bacterial sinusitis: either 1, 2
  • No improvement after 10 days, OR
  • Worsening after 5-7 days (the "double-worsening" pattern)

Key Physical Examination Findings

• Decongest the nasal mucosa first with topical vasoconstrictor to improve visualization 2
• Purulent exudate in the middle meatus is highly predictive of bacterial sinusitis 2
• Red, swollen nasal mucosa suggests infection (versus pale, boggy turbinates in allergic rhinitis) 2
• Check for maxillary dental tenderness (tooth roots project into the sinus floor) 2

Critical Pitfalls to Avoid

• Do not order X-rays for uncomplicated acute sinusitis—over-imaging leads to over-diagnosis because viral URIs commonly show sinus abnormalities 1, 2
• Do not treat based on imaging findings alone; antibiotics should be prescribed based on clinical symptoms, not radiographic mucosal thickening 6, 7
• Do not assume a negative X-ray rules out sinusitis in the ethmoid, frontal, or sphenoid sinuses—sensitivity is unacceptably low for these locations 3, 4
• If you must image for complications, skip X-rays entirely and proceed directly to CT 1, 5