Anatomic features of congenital nasolacrimal duct obstruction: a comparative computed tomography study.

Background: Investigating the anatomic features of congenital nasolacrimal duct obstruction (CNLDO) is crucial for understanding its etiology and guiding surgical management. This study aimed to compare the computed tomography (CT)-based features of the lacrimal sac fossa (LF) and nasolacrimal duct (NLD) in CNLDO patients against matched controls. Methods: This retrospective comparative observational study included 39 CNLDO patients who underwent cranial CT for preoperative evaluation, subdivided into 18 cases with chronic dacryocystitis and 21 cases without. For each patient, an age- and gender-matched control undergoing cochlear implantation CT assessment and screened to exclude craniofacial anomalies was enrolled. Measurements were conducted on CT images, including LF height and width, NLD height and width, frontal process thickness, and the presence of sinusitis. Comparisons were made among the obstructed, non-obstructed, and matched control sides. Results: Mean ages in the non-dacryocystitis and dacryocystitis groups were 2.58 and 3.08 years, respectively. In the non-dacryocystitis group, the narrowest NLD width on the obstructed side was significantly larger than that on the control side (3.38±0.70 vs. 2.82±0.47 mm, P=0.009). In the dacryocystitis group, the narrowest NLD, upper NLD, and LF widths on the obstructed side were significantly larger than those on the control side (3.90±0.70 vs. 2.82±0.47 mm; 4.72±1.10 vs. 3.43±0.79 mm; 5.57±1.40 vs. 4.48±0.89 mm; P<0.001, P<0.001, and P=0.034). No significant differences were found for other parameters or when comparing non-obstructed with control sides. Sinusitis prevalence did not differ among the groups. Conclusions: All obstructed sides of CNLDO exhibit an increase in NLD width. Besides, in CNLDO with chronic dacryocystitis, LF enlargement can also be observed in obstructed sides, with the anatomic changes more pronounced. We hypothesize that, in addition to elevated hydrostatic pressure, infectious factors are a significant cause of these structural expansions.