OP99 – Can Thyroid Ultrasonography Predict Substernal Extension and/or Tracheal Compression in Significantly Enlarged Thyroid Glands?

      Ziai, Hedyeh1; Lebo, Nicole L2; Kielar, Ania3; Odell, Michael J2 1 Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada 2 Department of Otolaryngology-Head and Neck Surgery, The Ottawa Hospital, Ottawa, ON, Canada 3 Department of Diagnostic Imaging, The Ottawa Hospital, Ottawa, ON, Canada   Background/Purpose: The determination of thyroid size is an important prerequisite for surgical planning in thyroidectomy. While ultrasonography (US) is the primary method used for imaging the thyroid, it is limited in cases with mediastinal extension due to overlying bone and artifacts. There are also some difficulties in assessing tracheal deformation with US. Objective: Determine whether US-defined thyroid volume predicts substernal extension and/or tracheal narrowing. Methods: Our tertiary care centre institutional database identified patients with thyroid nodules investigated with both US and Computed Tomography (CT).  Reviewers assigned scores for both substernal extension and tracheal compression using pre-established classification systems. Statistical analysis with ROC curve analysis was performed to find the US-determined thyroid volume threshold that is correlated with substernal extension and/or tracheal compression. Results: This study included 120 patients (mean age 63.4 years; SD±15.9; 67% female). Thirty-five patients (29%) had substernal extension. The mean US-detected thyroid gland volumes in patients with and without substernal extension were 77.0 and 18.8 cm3, respectively (p<0.001). 83% of patients with substernal extension had tracheal narrowing vs. 27% of patients without substernal extension (p<0.001). A cut-off gland volume of ?30 cm3 showed 89% sensitivity and 82% specificity for substernal extension (AUC=0.89). Similarly, using a ?30 cm3 threshold, 89% sensitivity and 67% specificity were obtained with significant tracheal narrowing (>50%)(AUC=0.81). Discussion/Conclusion: This study suggests that US volumes may be used as a predictor to identify those most at risk of substernal extension and tracheal compression, and who may benefit from pre-operative CT imaging for optimal surgical and anesthetic planning.


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