Quantitative CT Analysis of Nasal Septal Body and Inferior Turbinate Morphology in Allergic Rhinitis: Structural–Airway Relationships

Background/Objectives: Allergic rhinitis (AR) is characterized by dynamic mucosal congestion, yet the nasal septal body (NSB), inferior turbinate (IT), and adjacent airway passages have rarely been assessed together. We evaluated whether AR is associated with a multilevel structural–airway pattern while limiting confounding by marked septal deviation. Methods: This retrospective cross-sectional study included 301 adults with septal deviation < 8° (163 patients with clinically diagnosed AR and 138 participants in a clinically defined non-AR comparison group). Coronal computed tomography measurements included total transverse NSB width, dominant IT width, and adjacent airway widths. Between-group differences were evaluated using effect sizes and multivariable regression adjusted for age, sex, and septal deviation angle. Correlation, interaction, and sensitivity analyses assessed structure–airway relationships. Results: Patients with AR had greater NSB width (11.92 ± 1.81 vs. 10.80 ± 1.89 mm; Hedges’ g = 0.605) and dominant IT width (12.78 ± 1.69 vs. 10.41 ± 1.83 mm; g = 1.350), together with smaller adjacent airway widths. All four primary comparisons remained significant after Holm correction and adjustment (all p < 0.001). The NSB–IT correlation (rho = 0.257) was attenuated after adjustment for AR (partial rho = 0.089; q = 0.124), whereas inverse structure–airway associations persisted. A significant AR-status × IT-width interaction was observed for medial airway width (interaction q = 0.030). Conclusions: At the time of CT, patients with AR had greater NSB and IT widths and smaller corresponding regional airway dimensions, with a larger between-group morphometric difference at the IT level. These findings support a multilevel anatomical view of the nasal airway in AR, in which the NSB and IT are best interpreted together with their adjacent airway spaces rather than as isolated structures. Their clinical relevance, however, requires validation against symptoms and objective airflow measures.