Study design
This retrospective study included patients visiting the outpatient department of Otolaryngology Head and Neck Surgery, Shuang Ho Hospital, Taipei Medical University. Patients visited between January and April 2020 with a chief complaint wherein chronic rhinosinusitis was suspected. We selected cases according to inclusion criteria with a clinical diagnosis of chronic rhinosinusitis confirmed by high-resolution computed tomography (HRCT) scan of paranasal sinuses. Bilateral accessory maxillary sinus ostia were viewed in axial and coronal sections. (Figure 1). Images with suspicion of accessory maxillary sinus ostia in superior meatus were reconstructed by three-dimensional (3D) simulation to confirm the existence of accessory ostia (Figure 2). Patients who had systemic diseases such as cystic fibrosis, previous sinus surgery, acute sinusitis, maxillofacial trauma, inverted papilloma, cystic fibrosis, choanal atresia, or sinus anomalies were excluded. Finally, 159 patients were included for analysis.