What is the definition, types, and diagnosis of Chronic Rhinosinusitis (CRS)?

Chronic Rhinosinusitis: Definition, Types, and Diagnosis

Definition

Chronic rhinosinusitis is defined as the presence of two or more symptoms lasting ≥12 weeks, where at least one symptom must be either nasal blockage/obstruction/congestion OR nasal discharge (anterior/posterior nasal drip), with objective confirmation by endoscopy or CT imaging. 1

Core Diagnostic Criteria in Adults

The diagnosis requires both symptomatic and objective evidence 1:

Symptomatic criteria (≥2 symptoms for ≥12 weeks):

• Mandatory (at least one): Nasal blockage/obstruction/congestion OR nasal discharge (anterior/posterior drip) 1
• Optional: Facial pain/pressure OR reduction/loss of smell 1

Objective confirmation (at least one):

• Endoscopic findings: Nasal polyps in middle meatus, mucopurulent discharge from middle meatus, or edema/mucosal obstruction in middle meatus 1
• CT findings: Mucosal changes in paranasal sinuses (minimal thickening involving only 1-2 walls without ostial involvement is insufficient) 1

Diagnostic Criteria in Children

The pediatric definition differs by substituting cough for loss of smell 1:

Required symptoms (≥2 for ≥12 weeks):

• Mandatory (at least one): Nasal blockage/obstruction OR nasal discharge 1
• Optional: Facial pain/pressure OR cough (daytime and nighttime) 1

Objective confirmation: Same endoscopic or CT criteria as adults 1

Types and Classification

Primary Classification: Based on Nasal Polyps

CRS is fundamentally divided into two phenotypes based on endoscopic visualization 1:

1. CRS with Nasal Polyps (CRSwNP):

• Bilateral polyps endoscopically visualized in the middle meatus 1
• Traditionally associated with Type 2 inflammation, though significant heterogeneity exists 2
• After surgery (>6 months post-op): bilateral pedunculated lesions (not cobblestoned mucosa) 1

2. CRS without Nasal Polyps (CRSsNP):

• No visible polyps in middle meatus (assessed after decongestant if necessary) 1
• Traditionally associated with Type 1 inflammation, though mixed profiles are common 2
• Post-surgery: any mucosal disease without overt polyps 1

Critical distinction: This classification accepts polypoid changes within sinuses/middle meatus but excludes polypoid disease presenting in the nasal cavity to avoid overlap 1

Advanced Classification: Anatomic Distribution and Endotypes

The EPOS 2020 framework classifies CRS by anatomic distribution and inflammatory endotype 1:

Localized (Unilateral) CRS:

• Type 2 endotype: Allergic fungal rhinosinusitis (AFRS) 1
• Non-Type 2 endotype: Isolated sinusitis 1

Diffuse (Bilateral) CRS:

• Type 2 endotype: CRSwNP 1
• Non-Type 2 endotype: AFRS, central compartment atopic disease 1

Related Condition: Recurrent Acute Rhinosinusitis (RARS)

RARS is defined as ≥4 episodes per year with complete symptom-free intervals between episodes 1. This differs from CRS by the presence of symptom-free periods and duration <12 weeks per episode 1.

Diagnostic Approach

Clinical Diagnosis Algorithm

Step 1: Symptom Assessment

• Verify ≥2 symptoms present for ≥12 weeks 1
• Confirm at least one cardinal symptom (nasal obstruction OR discharge) 1
• Document allergic symptoms (sneezing, watery rhinorrhea, nasal itching, itchy watery eyes) 1

Step 2: Objective Confirmation

• Nasal endoscopy: Examine for polyps, mucopurulent discharge, or mucosal edema in middle meatus 1
• CT imaging: Document mucosal thickening, air-fluid levels, or opacification (exclude minimal thickening of 1-2 walls without ostial involvement) 1

Step 3: Exclude Secondary Causes 1

The following conditions should be excluded from general CRS diagnosis:

• Cystic fibrosis (sweat test or DNA alleles) 1
• Gross immunodeficiency (congenital or acquired) 1
• Primary ciliary dyskinesia 1
• Fungal balls and invasive fungal disease 1
• Systemic vasculitis and granulomatous diseases 1
• Cocaine abuse 1
• Neoplasia 1

Important Co-morbidities to Document

These conditions significantly impact treatment decisions and should be systematically assessed 1:

• NSAID-exacerbated respiratory disease (N-ERD): Positive provocation testing or clear history 1
• Asthma/bronchial hyperreactivity/COPD: Respiratory function tests 1
• Allergy: Specific serum IgE or skin prick testing 1
• Total serum IgE: Treatment effects may be influenced by IgE levels 1
• Eosinophil levels: Both blood and tissue 1

Common Diagnostic Pitfalls

Pitfall 1: Relying on symptoms alone - Symptoms have high sensitivity but low specificity, making objective findings mandatory 1. Overlap with allergic and non-allergic rhinitis leads to overestimation of CRS prevalence when diagnosis is symptom-based only 1.

Pitfall 2: Misinterpreting minimal CT changes - Minimal mucosal thickening involving only 1-2 sinus walls without ostial involvement is unlikely to represent true rhinosinusitis 1.

Pitfall 3: Assuming uniform inflammatory profiles - The traditional dichotomy of Type 2 inflammation in CRSwNP and Type 1 in CRSsNP is oversimplified; significant heterogeneity exists both between and within populations 2.

Pitfall 4: Inadequate duration assessment - Symptoms must persist for the full 12-week threshold; shorter durations with symptom-free intervals suggest RARS rather than CRS 1.

Research-Specific Definitions

For research purposes, CRS diagnosis should be based on phenotypes and endotypes, with consideration for previous surgery status 1. Bacteriology (antral tap, middle meatal culture) and radiology (CT) are advised but not obligatory for acute rhinosinusitis research 1.