What are the current evidence‑based guidelines for diagnosing and managing acute (≤4 weeks) and chronic (>12 weeks) sinusitis, including antibiotic selection, adjunctive therapies, imaging indications, and referral criteria?

Sinusitis Guidelines: Evidence-Based Diagnosis and Management

Diagnosis and Classification

Diagnose acute bacterial rhinosinusitis (ABRS) when symptoms persist ≥10 days without improvement, severe symptoms are present (fever >38.3°C with purulent discharge and facial pain), or "double worsening" occurs (initial improvement followed by worsening within 10 days). 1, 2

Acute Rhinosinusitis (<4 weeks)

• Viral rhinosinusitis (98-99.5% of cases): Symptoms <10 days, resolves spontaneously without antibiotics 2, 1
• Acute bacterial rhinosinusitis: Requires ≥10 days persistent symptoms OR severe presentation OR double worsening 1
• Key symptoms include purulent nasal discharge, nasal obstruction, facial pain-pressure-fullness, and decreased smell 1

Chronic Rhinosinusitis (>12 weeks)

• Requires ≥12 weeks of two or more symptoms: mucopurulent drainage, nasal obstruction, facial pain-pressure-fullness, or decreased smell 1
• Must document inflammation by: purulent mucus/edema in middle meatus, nasal polyps, OR radiographic evidence of sinus inflammation 1

Recurrent Acute Rhinosinusitis

• Defined as ≥4 episodes per year of ABRS with complete symptom resolution between episodes 1

Imaging Indications

Radiographic imaging is NOT recommended for uncomplicated acute rhinosinusitis. 1 Plain radiographs have significant false-positive and false-negative results 1.

When to Order Imaging:

• CT scan (without contrast) is indicated for: chronic rhinosinusitis diagnosis, recurrent acute rhinosinusitis, suspected complications (orbital/intracranial involvement), preoperative planning, or treatment failure 1
• Obtain CT ≥2 weeks after upper respiratory infection and ≥4 weeks after acute bacterial sinusitis treatment 1
• MRI with contrast for: suspected tumor, fungal sinusitis, skull base involvement, or intracranial extension 1

Antibiotic Selection for Acute Bacterial Rhinosinusitis

First-line: Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days (or until symptom-free for 7 days, typically 10-14 days total). 1, 2 This provides superior coverage against β-lactamase-producing H. influenzae and M. catarrhalis 1, 2.

Treatment Algorithm:

1. Start amoxicillin-clavulanate 875/125 mg twice daily 1, 2
2. Reassess at 3-5 days: If improving, continue until symptom-free for 7 days 1, 3
3. If no improvement at 3-5 days: Switch to high-dose amoxicillin-clavulanate (2g twice daily) OR respiratory fluoroquinolone 1

Second-Line Options (Treatment Failure):

• Levofloxacin 500-750 mg once daily for 10-14 days OR moxifloxacin 400 mg once daily 1, 4, 2
• These provide 90-92% clinical efficacy against multi-drug resistant S. pneumoniae and β-lactamase-producing organisms 1, 4

Penicillin-Allergic Patients:

• Non-anaphylactic allergy: Second- or third-generation cephalosporins (cefuroxime, cefpodoxime, or cefdinir) for 10 days 1, 4, 2
• Severe/anaphylactic allergy: Levofloxacin 500 mg once daily for 10-14 days 4, 2
• Avoid: Macrolides (azithromycin) due to 20-25% resistance rates for S. pneumoniae and H. influenzae 4
• Avoid: Trimethoprim-sulfamethoxazole due to 50% resistance rates for S. pneumoniae 4

Pediatric Dosing:

• Standard: Amoxicillin 45 mg/kg/day in 2 divided doses 2
• High-risk or treatment failure: Amoxicillin-clavulanate 80-90 mg/kg/day (amoxicillin component) with 6.4 mg/kg/day clavulanate in 2 divided doses 1, 2

Adjunctive Therapies

Prescribe intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily for all patients with acute or chronic rhinosinusitis. 1, 4, 2 These reduce mucosal inflammation and improve drainage with a number needed to treat of 14 4.

Additional Supportive Measures:

• Saline nasal irrigation to promote mucus clearance 1, 4
• Analgesics (acetaminophen or NSAIDs) based on pain severity 1, 4
• Short-term oral corticosteroids (5 days) for marked mucosal edema, nasal polyposis, or treatment failure 1, 4
• Adequate hydration, rest, warm facial packs, steamy showers, elevated head of bed 1

Therapies to Avoid:

• Antihistamines, decongestants, mucolytics: Only provide symptomatic benefit in selected cases; not routinely recommended 1

Chronic Rhinosinusitis Management

The role of antibiotics in chronic rhinosinusitis is controversial. 1 Treatment focuses on addressing underlying inflammatory disorders rather than infection 1.

Diagnostic Workup:

• Nasal endoscopy to visualize purulent discharge, edema, or polyps in middle meatus 1
• CT scan (coronal views) to document inflammation and assess ostiomeatal complex 1
• Test for modifying factors: allergic rhinitis, immunodeficiency (quantitative immunoglobulins, functional antibody tests, HIV), cystic fibrosis (sweat chloride, genetic testing), ciliary dyskinesia, GERD 1
• Allergy testing when allergic rhinitis is suspected 1

Treatment Approach:

• Intranasal corticosteroids twice daily as primary therapy 1
• Saline irrigation for symptom control 1, 4
• Systemic corticosteroids for chronic hyperplastic (non-infectious) sinusitis 1
• Prolonged antibiotics (3-6 weeks) only for chronic infectious sinusitis with attention to anaerobic coverage 1
• Treat underlying conditions: allergic rhinitis, GERD, immunodeficiency 1

Referral Criteria

Refer to otolaryngology or infectious disease when:

• No improvement after 7 days of appropriate second-line antibiotic therapy 1, 4, 2
• Worsening symptoms at any time during treatment 4, 2
• Suspected complications: facial swelling/erythema over sinus, visual changes, abnormal extraocular movements, proptosis, periorbital inflammation, intracranial involvement, abnormal neurologic signs 1
• Recurrent acute rhinosinusitis (≥3 episodes per year) 1, 4, 2
• Chronic rhinosinusitis refractory to medical management 1
• Need for functional endoscopic sinus surgery evaluation 1
• Immunocompromised patients or unusual opportunistic infections 1
• Complicating conditions: nasal polyps, asthma, aspirin sensitivity, allergic fungal disease, granulomas 1

Critical Monitoring Points

Reassess at 3-5 days: If no improvement, switch antibiotics or re-evaluate diagnosis 1, 4, 2

Reassess at 7 days: Confirm ABRS diagnosis if symptoms persist or worsen; consider complications or alternative diagnoses 1, 2

Instruct patients to return immediately for: severe headache, high fever, facial swelling, visual changes, or neurologic symptoms 1

Common Pitfalls to Avoid

• Do not prescribe antibiotics for viral rhinosinusitis (<10 days symptoms) 1, 2
• Do not use plain radiographs for diagnosis due to poor sensitivity/specificity 1
• Do not use first-generation cephalosporins (inadequate H. influenzae coverage) 4
• Do not use macrolides or trimethoprim-sulfamethoxazole as first-line due to high resistance rates 4
• Do not obtain CT during acute infection (wait ≥2 weeks after URI, ≥4 weeks after ABRS treatment) 1
• Do not assume chronic symptoms equal chronic infection (most chronic rhinosinusitis is inflammatory, not infectious) 1