A 38-year-old woman presents with a 3-week history of purulent nasal discharge, facial pain over the cheeks and forehead, and post-nasal drip. She reports low-grade fever (37.8°C) and denies recent upper respiratory infection. On examination, the nasal mucosa is edematous and pale, and palpation over the maxillary sinuses elicits tenderness. A non-contrast CT scan of the paranasal sinuses shows opacification of the maxillary and ethmoid sinuses with air-fluid levels. What is the most likely diagnosis?

Explanation

## Diagnosis: Acute Bacterial Sinusitis ### Clinical Presentation The patient presents with the cardinal features of acute bacterial sinusitis: - **Duration:** 3 weeks (acute phase is typically 4 weeks or less) - **Symptoms:** Purulent nasal discharge, facial pain, post-nasal drip, low-grade fever - **Examination findings:** Edematous nasal mucosa, sinus tenderness on palpation - **Imaging:** Air-fluid levels in maxillary and ethmoid sinuses (hallmark of acute infection) ### Key Diagnostic Criteria **High-Yield:** Acute bacterial sinusitis is diagnosed when symptoms persist for >7 days or worsen after initial improvement ("double sickening"). The presence of purulent discharge, fever, and imaging evidence of air-fluid levels strongly supports bacterial etiology. ### Pathophysiology 1. Viral upper respiratory infection → mucosal edema and impaired mucociliary clearance 2. Obstruction of sinus ostia → stasis of secretions 3. Secondary bacterial colonization (most common: *Streptococcus pneumoniae*, *Haemophilus influenzae*, *Moraxella catarrhalis*) 4. Acute inflammation with purulent exudate ### Imaging Findings | Finding | Acute Sinusitis | Chronic Sinusitis | |---------|-----------------|-------------------| | Air-fluid levels | Present | Absent | | Mucosal thickening | Mild to moderate | Marked (>4 mm) | | Bone remodeling | Absent | Present | | Duration of symptoms | <4 weeks | >12 weeks | **Key Point:** Air-fluid levels on CT are pathognomonic for acute infection and indicate active suppuration within the sinus cavity. ### Management Approach ```mermaid flowchart TD A[Acute bacterial sinusitis suspected]:::outcome --> B{Severe symptoms or complications?}:::decision B -->|No| C[Supportive care + saline irrigation]:::action C --> D{Improvement in 7 days?}:::decision D -->|Yes| E[Continue conservative management]:::action D -->|No| F[Start empiric antibiotics]:::action B -->|Yes or immunocompromised| G[Empiric antibiotics immediately]:::action F --> H[Amoxicillin-clavulanate or fluoroquinolone]:::action G --> H H --> I[Reassess at 48-72 hours]:::decision I -->|Improvement| J[Continue for 10-14 days]:::action I -->|No improvement| K[Consider imaging, specialist referral]:::urgent ``` **Clinical Pearl:** Most cases of acute sinusitis resolve with conservative management (saline irrigation, decongestants, analgesics) within 7–10 days. Antibiotics are reserved for severe cases, immunocompromised patients, or those failing conservative therapy.