Abstract: Objective To explore the risk grading method for benign thyroid nodules before microwave ablation and the clinical significance of risk grading. Methods This study was conducted among 527 patients undergoing ultrasound-guided microwave ablation of benign thyroid nodules between July, 2017 and December, 2020. Based on anatomic relationship of the thyroid nodules with the adjacent tissues, the ablation risk was classified into 4 levels: low, medium, high and extremely high risks. The incidence of severe complications and the rate of residual nodules following the ablation were recorded. Results In the patients graded to have low, medium, high and extremely high preoperative risks, the incidences of severe complications following the ablation were 0%, 0.88%, 2.41% and 6.78%, respectively, showing no significant differences among the different risk groups (P>0.05). The rates of postoperative residual nodules in the 4 risk groups were 1.59%, 6.14%, 14.43% and 71.19%, respectively, showing a significant difference between the low and medium risk groups and the high and extremely high risk groups (P<0.001). Conclusion Preoperative risk grading for thyroid nodular ablation can be helpful for prevention of severe complications during ablation and prediction of residual nodules after ablation.

Key words: thyroid nodules; microwave ablation; risk grading; complication