A 35-year-old man presents with a 12-day history of facial pain, purulent nasal discharge, and fever (38.8°C). On examination, tenderness is elicited on palpation over the cheek. A Waters view X-ray is obtained. The structure marked **A** in the diagram is noted to show opacification. Which of the following clinical features would MOST strongly support a diagnosis of acute bacterial rhinosinusitis (ABRS) in this patient, given the involvement of this sinus?

Explanation

## Why "Symptoms persisting >10 days without improvement or with initial improvement followed by worsening" is right The maxillary sinus (marked **A**) is the largest and most commonly involved sinus in acute bacterial rhinosinusitis (ABRS). Per IDSA and AAO-HNS guidelines, the key clinical features distinguishing ABRS from viral upper respiratory infection are: (1) symptoms lasting >10 days without improvement, and (2) "double sickening"—initial improvement followed by worsening. The Waters view (occipitomental projection) best visualizes the maxillary sinuses by projecting the petrous bones below them, allowing clear assessment of maxillary sinus involvement without overlap. In this case, the patient's 12-day history with fever ≥39°C and purulent discharge meets the diagnostic threshold for ABRS, particularly when maxillary sinus opacification is demonstrated (Dhingra ENT 7e; Harrison 21e Ch 198). ## Why each distractor is wrong - **"Symptoms lasting 5-7 days with mild rhinorrhea and nasal congestion"**: This timeline is typical of viral URI, which typically resolves by day 7–10. ABRS requires symptoms persisting >10 days or severe features at onset. This duration alone does not meet diagnostic criteria. - **"Symptoms lasting 3 days with clear nasal discharge and low-grade fever"**: A 3-day history is far too short to diagnose ABRS; viral URIs commonly present with clear discharge and low-grade fever. Bacterial sinusitis requires either >10 days of symptoms or severe features (fever ≥39°C, purulent discharge, facial pain ≥3–4 days) at onset. - **"Symptoms lasting 2 weeks with only post-nasal drip and no facial pain"**: While the 2-week duration exceeds 10 days, the absence of facial pain, purulent discharge, or fever makes bacterial sinusitis less likely. ABRS typically presents with facial pain/pressure over the involved sinus (in this case, maxillary), purulent rhinorrhea, and fever—not isolated post-nasal drip. **High-Yield:** Maxillary sinusitis on Waters view + symptoms >10 days (or "double sickening") + purulent discharge + fever ≥39°C = ABRS; viral URI typically resolves by day 7–10. [cite: Dhingra ENT 7e; Harrison 21e Ch 198; IDSA/AAO-HNS ABRS guidelines]