What are the steps for differential diagnosis and treatment of rhinosinusitis?

Differential Diagnosis of Rhinosinusitis

The differential diagnosis of rhinosinusitis requires distinguishing between acute viral, acute bacterial, chronic, allergic, and non-allergic forms based on symptom duration, pattern, and objective evidence of inflammation—with the critical distinction being that chronic rhinosinusitis cannot be diagnosed on symptoms alone and requires either nasal endoscopy or CT confirmation. 1

Classification by Duration and Pattern

Acute Rhinosinusitis (Symptoms <4 weeks)

• Acute viral rhinosinusitis (AVRS) is the most common form and should be presumed when symptoms last less than 10 days without worsening 2
• Acute bacterial rhinosinusitis (ABRS) should be suspected when: symptoms persist ≥10 days beyond onset of upper respiratory symptoms, symptoms worsen within 10 days after initial improvement, or symptoms are particularly severe in the first 3-4 days of illness (high fever ≥39°C, purulent nasal discharge, facial pain) 2
• The presence of purulent nasal discharge alone is insufficient for bacterial diagnosis—the temporal pattern is critical 3

Recurrent Acute Rhinosinusitis

• Defined as 2-4 isolated episodes of acute rhinosinusitis per year with complete resolution of symptoms between episodes 2
• Warrants investigation for underlying causes including allergic rhinitis, cystic fibrosis, immunologic deficiency, ciliary dyskinesia, or anatomic abnormalities 2

Chronic Rhinosinusitis (Symptoms ≥12 weeks)

• Requires at least 2 of 4 cardinal symptoms: nasal obstruction/congestion, mucopurulent drainage (anterior or posterior), facial pain/pressure/fullness, and reduction or loss of smell 1, 2
• Critical distinction: Symptoms alone are insufficient—objective evidence of inflammation via nasal endoscopy (purulent mucus or edema in middle meatus, nasal polyps) OR CT imaging is mandatory for diagnosis 1, 2
• Decreased sense of smell is more characteristic of chronic than acute rhinosinusitis 2

Key Differential Diagnoses to Consider

Allergic Rhinitis

• Characterized by IgE-mediated inflammation with nasal itching, sneezing, clear rhinorrhea, and often ocular symptoms 1
• Diagnosis confirmed by positive skin testing or specific IgE blood tests correlating with symptom triggers 2
• Symptoms typically seasonal or related to specific environmental exposures 2

Non-Allergic Rhinitis

• Includes vasomotor rhinitis, non-allergic rhinitis with eosinophilia syndrome (NARES), and rhinitis medicamentosa 1
• Vasomotor rhinitis presents with persistent nasal congestion and clear discharge triggered by irritants, temperature changes, or strong odors 2, 1
• Rhinitis medicamentosa results from overuse of topical nasal decongestants and requires discontinuation with intranasal or systemic corticosteroids 2

Allergic Fungal Rhinosinusitis (AFRS)

• Requires presence of allergic mucin (thick, viscous mucus with dense eosinophils), nasal polyps, and evidence of fungus-specific IgE by skin test or blood test 2
• CT imaging typically shows characteristic heterogeneous opacification 2
• No histologic evidence of invasive fungal disease 2

Chronic Hyperplastic Eosinophilic Sinusitis

• Non-infectious form marked by preponderance of eosinophils and mixed mononuclear cells with relative paucity of neutrophils 2
• Does not respond to antibiotics and may require systemic corticosteroids 2

Diagnostic Algorithm

Step 1: Assess Duration and Temporal Pattern

• <10 days without worsening: Presumed viral, supportive care only 2
• ≥10 days OR worsening after initial improvement OR severe onset: Consider bacterial, proceed to Step 2 2, 3
• ≥12 weeks: Chronic rhinosinusitis, requires objective confirmation (proceed to Step 3) 1

Step 2: Evaluate for Bacterial Infection (Acute Cases)

• Four findings significantly increase likelihood of bacterial cause: double sickening pattern, purulent rhinorrhea, ESR >10 mm/hour, and purulent secretion in nasal cavity on examination 3
• C-reactive protein and ESR are somewhat useful but not required for uncomplicated cases 3
• Radiography is NOT recommended for uncomplicated acute rhinosinusitis 3

Step 3: Obtain Objective Evidence (Chronic Cases)

• Nasal endoscopy is superior to anterior rhinoscopy for evaluating middle meatus and ostiomeatal complex 1, 2
• Look for purulent mucus, edema in middle meatus/ethmoid region, or nasal polyps 2, 1
• CT imaging should be reserved for: failure to respond to appropriate medical therapy, suspected complications, pre-surgical planning, or when diagnosis is uncertain 1, 2
• CT is particularly helpful for diagnosing allergic fungal rhinosinusitis 2

Step 4: Identify Underlying Causes

• Allergy testing (skin tests preferred over in vitro IgE) when history suggests seasonal or environmental triggers 1, 2
• Consider testing for immunodeficiency (quantitative IgG, IgA, IgM; specific antibody responses) in patients with recurrent infections, associated otitis media, bronchitis, or prior failed surgeries 2
• Nasal cytology may identify eosinophilic patterns suggesting NARES 2
• Consider cystic fibrosis, ciliary dyskinesia, or anatomic abnormalities in recurrent cases 2

Common Pitfalls to Avoid

• Do not diagnose chronic rhinosinusitis on symptoms alone—objective evidence via endoscopy or CT is mandatory 1, 2
• Do not order CT for uncomplicated acute rhinosinusitis—diagnosis is clinical 3, 2
• Do not assume purulent discharge equals bacterial infection—temporal pattern (≥10 days or worsening) is more important 2, 3
• Do not overlook rhinitis medicamentosa in patients using topical decongestants—requires specific management with discontinuation 2
• Do not miss comorbid conditions (asthma, immunodeficiency, ciliary dysfunction) that modify management 1, 2
• Nasal endoscopy is superior to anterior rhinoscopy but often overlooked—it provides better visualization of middle meatus and ostiomeatal complex 1, 2

When to Refer to Specialist

Consultation with allergist/immunologist or otolaryngologist is indicated for: 2

• Prolonged manifestations despite appropriate therapy
• Complications (orbital or intracranial extension, nasal polyps)
• Comorbid asthma or chronic sinusitis
• Need for systemic corticosteroids
• Suspected immunodeficiency or anatomic abnormalities
• Consideration of immunotherapy or surgical intervention
• Symptoms persisting after maximal medical therapy 3