Diagnostic Utility of Upper Airway Ultrasonography in Adults with Suspected Obstructive Sleep Apnea: A Systematic Review

Background: Ultrasonographic assessment of the upper airway has emerged as a non-invasive method for evaluating obstructive sleep apnea (OSA), offering advantages including wide accessibility and absence of ionizing radiation. However, the diagnostic validity and standardized screening thresholds for ultrasonographic parameters remain unclear. Methods: A systematic literature search was conducted in PubMed, Scopus, and ScienceDirect from database inception to February 2026. Eligible studies enrolled adults with suspected OSA, used in-laboratory polysomnography (PSG) as the reference standard, and assessed upper-airway structures using ultrasonography. Studies reporting diagnostic performance metrics (sensitivity, specificity, AUC, or diagnostic thresholds) or quantitative associations with apnea–hypopnea index (AHI) were included. Risk of bias was assessed using QUADAS-2. Owing to methodological heterogeneity, findings were synthesized qualitatively. Results: Six studies (n = 473 participants) met the inclusion criteria. Evaluated parameters included tongue base thickness, lingual artery distance, lateral pharyngeal wall thickness, dynamic airway dimensional changes, and tongue stiffness. Three studies reported threshold-based diagnostic performance, although only one provided a complete diagnostic contingency table. Dynamic retropalatal percentage change demonstrated the highest diagnostic performance (AUC up to 0.989; sensitivity 97%; specificity 93.3%). Other studies demonstrated significant morphologic associations with OSA severity but lacked externally validated diagnostic thresholds. Conclusions: Ultrasonographic upper-airway assessment demonstrates promising structural and functional correlates of OSA. However, robust diagnostic accuracy evidence and standardized thresholds remain limited. Further prospective studies with standardized acquisition protocols and predefined diagnostic thresholds are required before ultrasound can be incorporated into routine OSA screening pathways.