The 10-day mark is a good way to diagnose not only acute rhinosinusitis but also adenoiditis, as confirmed by endoscopy.

Acute rhinosinusitis (ARS) usually presents with respiratory complaints that persist for more than 10 days with no sign of improvement. This 10-day mark is considered to separate simple upper viral respiratory infection from ARS. Thus, the aim of the study was to evaluate a group of children with suspected ARS by performing nasal endoscopy.This cross-sectional study evaluated 287 consecutive children (152 males and 135 females, aged between 2 and 15 years), in whom ARS was suspected. A detailed clinical history was recorded for each patient and a thorough physical examination was carried out by an allergist-paediatrician. Patients were also evaluated by an ENT specialist who performed nasal endoscopy.Endoscopy confirmed the clinical diagnosis of rhinosinusitis in 256 patients (89.2\%). Isolated rhinosinusitis was diagnosed in 80.85\% of cases (207 patients), whereas it was associated with adenoiditis in 49 (19.15\%) children. Twenty patients had adenoiditis alone (7\%). The distribution of the isolated and combined diagnoses differed significantly between age groups (p=0.015), particularly between the youngest and oldest group (post hoc test p=0.005).This study suggests that the endoscopy is a valuable tool in diagnosing children with suspected ARS and with adenoiditis too. Moreover, the age influences the diseases' pattern.