Fusiform enlargement of the nasolacrimal canal: a rare anatomic variation.

To determine the standard width and shape of the nasolacrimal canal (NLC) in the coronal plane, a retrospective review of 950 coronal paranasal CT sections was undertaken. The coronal diameter of NLC was measured at its upper and lower ends and anomalies in its configuration noted. The mean diameters of the NLC were 4.8 +/- 1.2 mm and 4.7 +/- 1.1 mm on the right and left sides, respectively. There was no difference in the mean NLC diameter between the right and left sides, upper and lower portions or males and females. In two cases, an abnormal dilation of the NLC at its inferior portion was encountered. A marked enlargement of the NLC can occur in the absence of a neoplastic or obstructive process and may be detected as an isolated finding representing idiopathic or congenital enlargement. Segmental NLC dilatation is not always an indicator of pathology, particularly in asymptomatic cases, and should be considered a rare anatomic variation.