What is the most likely diagnosis for a patient with chronic coryza and easy fatigue, with a normal complete blood count, chest radiograph, and Waters‑view sinus X‑ray?

Chronic Rhinosinusitis (CRS) Without Nasal Polyps

The most likely diagnosis is chronic rhinosinusitis (CRS) without nasal polyps, presenting as a chronic inflammatory condition that is not adequately visualized on Waters view radiography due to the limited sensitivity of plain films for detecting mucosal disease.

Why Standard Imaging Appears Normal

• Waters view sinus radiography has poor sensitivity for detecting chronic rhinosinusitis, with studies showing that mild-to-moderate mucosal thickening—the hallmark of CRS—is often a nonspecific finding that may not be appreciated on plain films 1.
• Plain radiographs demonstrate only 60% of sinusitis cases when looking for specific findings like air-fluid levels or complete opacification, missing the majority of chronic inflammatory changes 2.
• Standard radiography cannot adequately visualize the ethmoid sinuses and ostiomeatal complex, which are frequently involved in CRS, and ethmoid involvement without maxillary sinus disease occurs in approximately 20% of patients 1.
• Up to 40% of symptomatic adults with CRS show mucosal thickening and sinus abnormalities on CT that are completely missed on plain radiography 2.

Clinical Diagnosis of CRS

• CRS is defined by the presence of at least two cardinal symptoms persisting for 12 or more weeks: (1) nasal congestion/blockage, (2) anterior or posterior mucopurulent drainage (chronic coryza), (3) facial pain/pressure/fullness, and (4) hyposmia 1, 3, 4.
• The chronic fatigue ("easy fatigability") you describe is a well-recognized systemic manifestation of CRS, resulting from chronic inflammation and poor sleep quality related to nasal obstruction 1, 3.
• A normal CBC is expected in CRS, as this is a localized inflammatory condition rather than a systemic infection, distinguishing it from acute bacterial sinusitis 1, 3.

Why CT Is the Appropriate Next Step

• CT of the sinuses is the optimal imaging technique for evaluating CRS and should be obtained when symptoms persist despite initial treatment or when physical examination findings are equivocal 1.
• Noncontrast coronal CT can define nasal anatomy precisely and detect mucosal thickening, polyps, and ostiomeatal complex obstruction that are invisible on plain radiography 1, 2.
• The American College of Radiology and multiple rhinosinusitis guidelines recommend CT imaging after initial clinical examination and chest radiography when upper airway cough syndrome (UACS) or CRS is suspected as a cause of chronic cough 1.
• CT findings showed abnormalities in 66% of children with chronic cough, though these must be interpreted carefully given that 18-82% of asymptomatic individuals may have incidental sinus findings 1.

Diagnostic Algorithm

• Obtain nasal endoscopy to visualize the middle meatus and ethmoid region for purulent drainage, mucosal edema, or polyps—this provides objective evidence required for definitive CRS diagnosis 1.
• If nasal endoscopy shows mucosal inflammation or purulent secretions in the middle meatus, the diagnosis of CRS is confirmed without need for immediate CT 1.
• If nasal endoscopy is normal but symptoms persist, proceed to CT imaging, as up to 35% of patients with CRS have normal endoscopic findings yet show disease on CT 1.
• CT should be performed using fine-cut (≤1mm) coronal images to optimally evaluate the ostiomeatal complex and ethmoid sinuses 1.

Treatment Approach

• First-line maintenance therapy consists of intranasal corticosteroids (e.g., mometasone or fluticasone) combined with daily nasal saline irrigation 3, 4.
• For acute exacerbations with purulent drainage, consider a 2-4 week course of antibiotics targeting common pathogens (amoxicillin-clavulanate or doxycycline), though the role of antibiotics in chronic maintenance is limited 4, 5.
• Short courses (5-7 days) of oral corticosteroids may be added for severe exacerbations, though evidence for routine use is limited 3, 4.

Critical Pitfalls to Avoid

• Do not rely on Waters view or standard sinus radiography to exclude CRS—these films miss the majority of chronic inflammatory changes and cannot visualize the ethmoid sinuses adequately 1, 2.
• Do not assume normal imaging rules out CRS when clinical symptoms are classic; symptoms alone have only 37-73% sensitivity compared to CT findings, but the diagnosis remains clinical when supported by endoscopy 1.
• Do not order CT as a first-line test before attempting empiric medical therapy; guidelines recommend CT only after failed initial treatment or when considering surgical intervention 1.
• Do not overlook the need for objective evidence (endoscopy or CT) to confirm the diagnosis, as symptom-based diagnosis alone leads to overtreatment and unnecessary antibiotic use 1.