Prevalence of thyroid incidentalomas from 1995 to 2016: A single-center, retrospective cohort study

Background: Incidental detection of thyroid nodules on nonthyroid imaging may contribute to increased diagnosis of thyroid cancer. We investigated the prevalence of thyroid incidentalomas across imaging modalities among a predominately male veteran population. Methods: Thyroid nodules were identified on nonthyroid-directed radiology reports using natural language processing. All reports from 1995 to 2016 for chest computed tomography (CT), carotid ultrasound (US), and neck magnetic resonance imaging (MRI) were reviewed. Individuals with multiple studies were included at their initial study and duplicates removed. Results: A total of 25 763 carotid US, 23 526 chest CTs with contrast, 39 262 noncontrast chest CTs, and 9503 MRIs were reviewed. With duplicates removed, 14 642 carotid US, 12 923 chest CTs with contrast, 17 416 noncontrast chest CTs, and 6926 MRIs were included. Mean age was 66.2 years and 1834 were female (3.53%). Thyroid nodules were reported on 0.84% carotid US, 3.45% MRIs, 5.84% chest CTs with contrast, and 5.14% noncontrast chest CTs. Women had a higher rate of thyroid nodules on MRI (6.46% vs 3.20%, P = .003), chest CT with contrast (9.80% vs 5.72%, P = .007), and noncontrast chest CT (8.77% vs 5.02%, P = .002), but not on carotid US (1.99% vs 0.81%, P = .12). Incidentaloma prevalence increased with age on MRI, chest CT with or without contrast, but not on carotid US, and were more commonly reported from 2007 to 2016 compared to before 2007 across all modalities. Conclusions: Thyroid incidentalomas are commonly reported, are more common among women, and increase with age. The rate of reported incidental thyroid nodules is increasing, likely contributing to the increase in thyroid cancer.