Incidental detection of acquired unilateral nasolacrimal duct obstruction on I-131 whole body scan following I-131 therapy for thyroid cancer: a case report

Background Radioactive iodine 131 (I-131) is used in the treatment of differentiated thyroid cancer after thyroidectomy; however, its accumulation in non-thyroidal regions may give false positive results on iodine whole body scan (WBS).

Only a few cases of radioiodine uptake in the orbital region in patients with thyroid cancer have been reported, which could be due to metastasis or false positive causes resulting from contamination or inflammatory etiology.

Case presentation We describe a case of 49-year-old male with history of papillary thyroid carcinoma.

The follow-up I-131 whole body scan showed a focus of increased radiotracer uptake in the region of left orbit.

Correlative single photon emission computed tomography (SPECT-CT) showed that uptake was due to stenosis of the left nasolacrimal duct causing obstructive symptoms on left side.

Dacryoscintigraphy also demonstrated significant obstruction of left nasolacrimal system.

Conclusions The nasolacrimal duct obstruction is a rare adverse event after I-131 therapy that can result in an accumulation of radioiodine on whole body scan, mimicking metastasis.

The use of additional spot views and SPECT-CT images along with thyroglobulin levels can help physicians in clarifying the situation in these uncertain cases.