Topographic and anatomical features of the nasolacrimal duct obstruction due to radioiodine treatment.

PURPOSE: To investigate the topographic and anatomical features of secondary acquired nasolacrimal duct obstruction (SALDO) due to radioiodine therapy.

METHODS: Dacryocystography-computed tomography (DCG-CT) scans of the nasolacrimal ducts in 64 cases with SALDO due to radioiodine therapy and in 69 cases with primary acquired nasolacrimal duct obstruction (PANDO) were studied. The anatomical site of obstruction was located, and morphometric characteristics of the nasolacrimal ducts were calculated: volume, length, and average sectional area. The statistical analysis was performed using the t-criterion, ROC analysis, and the odds ratio (OR).

RESULTS: The mean nasolacrimal section area was 10.7 ± 0.8 mm2 in patients with PANDO and 13.2 ± 0.9 mm2 in patients with SALDO due to radioiodine therapy (p = 0.039); the AUC value in ROC analysis for this parameter was 0.607 (p = 0.037). The development of "proximal" obstruction including lacrimal canaliculi obstruction and obstruction at the site of the lacrimal sac was 4.076 times more likely (CI: 1.967-8.443) in patients with PANDO than in patients with SALDO due to radioactive iodine exposure.

CONCLUSIONS: By comparing CT scans of the nasolacrimal ducts, we observed that in SALDO obstruction due to radioactive iodine therapy is predominantly "distal," while in PANDO it is more often "proximal." The development of obstruction within SALDO is followed by more pronounced suprastenotic ectasia.