Intranasal anatomy of the nasolacrimal sac in endoscopic dacryocystorhinostomy.

Intranasal surface anatomy is fundamental to the technique of endoscopic dacryocystorhinostomy. In the current literature the lacrimal sac is described as being situated anterior to the anterior end of the middle turbinate with between 0% and 20% of the sac above the insertion of the middle turbinate on the lateral nasal wall (the axilla of the middle turbinate). The aim of this study was to use CT dacryocystograms (DCGs) and CT scans to establish the relationship of the lacrimal sac to the lateral nasal wall. Forty-seven individual lacrimal sacs were measured in relation to the common canaliculus, and 76 were measured in relation to the insertion of the middle turbinate. Measurements taken from the long axis of the sac showed the mean height of the sac above the middle turbinate insertion was 8.8 mm (SD = 0.2, 95% CI = 1.3) and below it was 4.1 mm (SD = 2.3, 95% CI = 1.1). The average measurement of the sac above the com-mon canaliculus on CT DCGs was 5.3 mm (SD = 1.7, 95% CI = 0.56), whereas the average measurement below the common canaliculus was 7.7 mm (SD = 2, 95% CI = 1.3) (n = 47 CT DCGs). The findings in this study show that a major portion of the sac is locat-ed above the insertion of the anterior end of the middle turbinate and, in addition, that a significant part of the sac lies above the entry point of the common canaliculus. Knowledge of these findings can ensure that the sac is adequately exposed during dacryocystorhinostomy by removal of sufficient bone and mucosa above the anterior insertion of the middle turbinate.