RESULTS
During the study period, the overall percentage of ESS procedures for SFB in our institute was 11.58% (713/6159). The annual incidence of SFB demonstrated an increasing trend since 2005, increased to over 10% since 2008. Twenty-five (3.51%) patients with SFB had bilateral lesions. Among the unilateral FBs, single sinus involvement was observed in 679 (98.69%) cases; the maxillary sinus was involved in the majority of cases (86.05%). The distribution of sinus involvement by FBs is shown in Figure 1 .
The clinical characteristics of the 592 patients with unilateral MSFB are shown in Table 1 . The mean age of patients was 57.4 (±13.53) (range: 18 to 90) years. Female predominance was seen in our series, with 380 female patients (64.63%) and 208 males (35.37%); 115 (19.56%) patients had comorbid medical conditions that may weaken the immune system, including diabetes mellitus (DM), liver cirrhosis, autoimmune disorders, end-stage renal disease, and bronchial asthma. Among them, DM was the most common comorbidity (14.80%). Recurrence was seen in 11 (1.87%) patients; 7 (1.19%) cases of complicated FB including facial cellulitis and orbital complications were observed. Fungal culture was performed in 211 cases (35.64%); among them, 29 (13.74%) showed positive results. The main species (14/29, 48.28%) was Aspergillus.
On the CT scan images, 386 cases (65.65%) showed complete opacification of the maxillary sinus, 462 cases (78.57%) had IH, and 119 cases (20.24%) had adjacent maxillary odontogenic pathology. The clinical characteristics of MSFB with and without IH were compared to evaluate the relationship between IH on CT, odontogenic pathology, and the degree of opacification; the results have been presented in Table 2 . Multivariate logistic regression analysis showed complete opacification on CT was less common in MSFB without IH (OR = 0.617; P = .025). Compared to those with IH, MSFB without IH was significantly more common in males (OR = 2.496; P < .0001), in those with diabetes mellitus (DM) (OR = 2.094; P = .010) and adjacent maxillary odontogenic pathology (OR = 1.697; P = .030) (Table 3) .
The female-to-male ratio in each decade of age was further analyzed in the two study groups; the results have been shown in Figure 3 . Female predominance was seen in all MSFB cases. The overall female-to-male ratio was highest at 51-60 years (2.02) and the ratio rose to 2.60 in the MSFB with IH group in the same age range. In contrast, female predominance was not seen in the MSFB without IH group. The difference between the 51-60 and 61-70 years groups was most significant.