Relationship of the anterior ethmoid sinus to the lacrimal sac: a computed tomography study

•The agger nasi is medial to the lacrimal sac in most patients.•The agger nasi can be considered an anatomical key point in endoscopic DCR.•The right and left sides of each patient have similar anatomy. To analyze the anatomical relationship between the lacrimal sac and the agger nasi cell on Computed Tomography (CT); to correlate the right and left sides on each scan. CT scans of adult patients were reviewed for pneumatization of the agger nasi and its relationship to the lacrimal sac. The degree of agreement between the right and left sides was also evaluated. A total of 130 CT scans were examined. An agger nasi cell was found medial to the lacrimal sac in 59.23% of scans. On 86.15% of scans, pneumatization was similar on both sides. The agger nasi air cell is located medial to the lacrimal sac in more than half of individuals. The right and left sides exhibit the same pneumatization pattern in approximately 80% of cases. 4.