Beyond direct visualization: a comparative analysis of computed tomography dacryocystographic features in dacryolithiasis, lacrimal sac cysts, and primary acquired nasolacrimal duct obstruction

Abstract

Background: Dacryoliths occur in approximately 5.8-18% of patients undergoing dacryocystorhinostomy (DCR), but conventional diagnostic methods often fail to distinguish them from other causes of nasolacrimal duct obstruction (NLDO). This study aimed to analyze the characteristic features of dacryoliths on computed tomography dacryocystography (CT-DCG) and to establish imaging criteria for their differential diagnosis from lacrimal sac cysts and primary acquired nasolacrimal duct obstruction (PANDO).

Methods: In this retrospective case-control study, CT-DCG images from 54 patients (18 with surgically confirmed dacryoliths, 18 with lacrimal sac cysts, and 18 with PANDO) were analyzed. The assessment included lacrimal sac dimensions, contrast distribution patterns, and characteristic imaging features. For each case, the extent of contrast filling, surface irregularities, and presence of calcification were evaluated. Intraoperative findings and histopathological results were documented for dacryolith cases.

Results: Analysis of contrast distribution patterns on CT-DCG revealed significant differences between groups (P<0.01), with dacryolith cases showing characteristic moderate contrast filling (63.30%±20.43%), significantly different from the minimal filling in lacrimal sac cysts (29.44%±11.77%) and near-complete filling in PANDO cases (80.14%±15.46%). Dacryoliths demonstrated characteristic imaging features including surface filling defects (82.4%), peripheral calcification (64.7%), and density interface lines (23.5%). Lacrimal sac dimensions showed significant differences in both transverse and anteroposterior (AP) diameters (P<0.01), primarily due to enlargement in the lacrimal sac cyst group, while dacryolith and PANDO groups showed comparable measurements. Intraoperatively, combined sac-duct involvement was most common (44.4%), and histopathological examination revealed periodic acid Schiff-positive staining in 38.89% of dacryolith cases.

Conclusions: CT-DCG revealed characteristic contrast distribution patterns in dacryolithiasis, with moderate contrast filling that differed significantly from the filling of both lacrimal sac cysts and PANDO. When combined with surface filling defects, peripheral calcification, or density interface lines, these imaging features may serve as valuable diagnostic indicators for preoperative detection of dacryoliths.

Keywords: Dacryolith; computed tomography dacryocystography (CT-DCG); lacrimal sac cyst; mucopeptide concretions; primary acquired nasolacrimal duct obstruction (PANDO).

Figure 1

Representative CT-DCG images demonstrating characteristic features and measurement methods. (A) Measurement methodology: red single-headed arrows clearly delineate the lacrimal sac boundary; the black horizontal double-headed arrow indicates the maximum transverse diameter measured at the widest point of contrast enhancement; the black vertical double-headed arrow shows the AP diameter measured perpendicular to the transverse axis; the red double-headed arrow demonstrates the vertical height of the contrast fluid level within the sac. (B-F) Characteristic imaging features: (B) surface filling defect (white arrow) at the contrast-air interface. (C) Peripheral calcification (white arrow) along the sac wall. (D) Superior air bubble (white arrow). (E) Lateral wall enhancement (white arrow). (F) Density interface line (white arrow) within the contrast-filled sac. AP, anteroposterior; CT-DCG, computed tomography dacryocystography.

Figure 2

Intraoperative endoscopic findings of dacryoliths during DCR surgery. (A) Oval dacryolith visible within the lacrimal sac after initial exposure. (B) Combined dacryolith traversing both the lacrimal sac and nasolacrimal duct. (C) Irregular dacryolith extending from the nasolacrimal duct. (D) Multiple round dacryoliths in aggregate formation encountered during surgical exploration. DCR, dacryocystorhinostomy.

Figure 3

Schematic representation and corresponding CT-DCG images of the contrast distribution patterns in three study groups. Group 1 (dacryolith): (A) schematic drawing showing moderate contrast filling (red) with stone presence (yellow) and (B) the corresponding CT-DCG image demonstrating surface filling defects (red arrows). Group 2 (lacrimal sac cyst): (C) schematic illustration depicting minimal contrast filling limited to the inferior sac and (D) the representative CT-DCG image. Group 3 (PANDO): (E) schematic diagram showing near-complete contrast filling of lacrimal sac and (F) the corresponding CT-DCG image demonstrating a characteristic complete filling pattern. CT-DCG, computed tomography dacryocystography; PANDO, primary acquired nasolacrimal duct obstruction.