Discussion

We found a unilateral maxillary sinus opacification rate of 9 per cent. Higher rates of 14–23 per cent have been reported,^{Reference Lee4,Reference Chen, Chen, Chang and Huang5} although these studies included only patients who underwent surgery. Others reporting a lower rate of 2.5 per cent used a stricter definition of complete unilateral maxillary sinus opacification.^{Reference Ahsan, El-Hakim and Ah-See7} Chen et al.^{Reference Chen, Su and Yeow8} identified a rate of 10.7 per cent by including scans with both partial and complete opacification, as well as patients who did not undergo surgery, similar to our study methodology.

Neoplasia represented 2 per cent of patients who had unilateral maxillary sinus opacification in our series. Chen et al.^{Reference Chen, Su and Yeow8} found a similarly low neoplasia rate of 3.9 per cent in 76 patients. However, most other studies report considerably higher rates, ranging from 11 per cent (n = 64),^{Reference Kaplan and Kountakis9} 15.1 per cent (n = 116),^{Reference Chen, Chen, Chang and Huang5} 19.8 per cent (n = 121),^{Reference Lee4} 20.2 per cent (n = 114),^{Reference Salami10} to 34 per cent (n = 110).^{Reference Eckhoff, Cox, Luk, Maidman, Wise and DelGaudio1} These studies had obtained histopathological diagnoses and therefore the samples represented study populations that had all undergone operative management. Selection bias may have caused an overestimation of the neoplasia rate. Our study mitigated this bias by including patients who did not have surgical intervention in the denominator of our rate calculation. Interestingly, two studies that also included patients without histopathological findings reported high neoplasia rates of 30–34.4 per cent.^{Reference Zahedi, Mohamed, Husain, Kew and Gendeh11,Reference Rudralingam, Jones and Woolford12} However, the number of CT scans requested in both of these studies was vastly lower per unit of time than in our study. This indicates that the clinician threshold for scanning may be an important confounding factor in the detection of neoplasia.

One case of lymphoma was detected in our series. This patient presented with a unilateral left-sided nasal mass and had an incidental finding of unilateral maxillary sinus opacification on the contralateral side. This case was not included in our reported rate of neoplasia as the unilateral maxillary sinus opacification itself did not represent a tumour. This case draws attention to the notion that localised pathology on one side of the nasal cavity does not protect the contralateral sinuses from an inflammatory process. This phenomenon has previously been highlighted in cases of mycetoma and mucocele.^{Reference Kaplan and Kountakis9}

Functional endoscopic sinus surgery was carried out for chronic rhinosinusitis (35 per cent), odontogenic infection (56 per cent), and all cases of antrochoanal polyp, inverted papilloma and lymphoma. The rationale for surgery was probably therapeutic for inflammatory conditions, and diagnostic in cases where neoplasia had to be ruled out. However, we cannot be certain about the clinicians’ reasoning behind the surgery given the retrospective nature of our study.

The two-year follow-up data did not reveal any missed cases of malignancy, although our data collection methodology was within the confines of a retrospective observational study.

The patients with unilateral chronic rhinosinusitis and odontogenic infection who did not undergo FESS were diagnosed on clinical grounds. The diagnosis of unilateral chronic rhinosinusitis in patients who were managed non-operatively was based on the same criteria for chronic rhinosinusitis, according to clinical, endoscopic and CT findings, as defined in the European Position Paper on Rhinosinusitis and Nasal Polyps 2020.^{Reference Fokkens, Lund, Hopkins, Hellings, Kern and Reitsma3}

The nine diagnoses of odontogenic infection were obtained by the following means: five were based on the CT report affirming dental pathology; one was diagnosed following recognition of dental pathology on the CT images by the otolaryngologist; two were diagnosed by general dental practitioners and referred to ENT following persistent symptoms after dental extraction; and one was diagnosed after referral to an oral and maxillofacial surgeon because of treatment failure after FESS.

Overall, an oral examination was performed in only 4 of the 52 patients (8 per cent) in our series. The CT reports commented on positive or negative dental findings in only 5 out of the 52 cases (10 per cent) of unilateral maxillary sinus opacification. This indicates that odontogenic infection was underappreciated by both otolaryngologists and radiologists. Our reported rate of odontogenic infection may be an underestimate, and it is possible that some odontogenic infection cases were mistaken for unilateral chronic rhinosinusitis. Turfe et al.^{Reference Turfe, Ahmad, Peterson and Craig13} also identified poor reporting of dental findings in 66 per cent of CT sinus scans in their series of odontogenic sinusitis. Collaboration between otolaryngologists and dental practitioners leads to a dramatic rise, up to 73 per cent, in the diagnosis of odontogenic infection in unilateral maxillary sinus opacification cases.^{Reference Matsumoto, Ikeda, Yokoi and Kohno14} A shared care model for unilateral maxillary sinus opacification should be encouraged, as recognition of odontogenic infection then allows the dental pathology to be addressed, which increases treatment success compared to FESS alone.^{Reference Gâta, Toader, Valean, Trombitaș and Albu15}