Objective To analyze the effect of different retained dosage of lauromacrogol within the thyroid cyst in the sclerotherapy of thyroid cysts.Methods A total of 200 patients with thyroid cysts,who were admitted to the Longyan Municipal First Hospital of China between August 2020 and August 2021,were enrolled in this study.The patients were randomly and equally divided into group zero(suctioning out all the amount of the injected lauromacrogol),and,according to the percentage of the retained lauromacrogol dosage to the total cystic fluid,group 10%,group 20%,group 30%and group 50%,with 40 patients in each group.Thyroid color ultrasound was reviewed at 1,3,6,and 12 months after treatment.The changes of capsule volume,curative efficacy,influencing factors,and adverse reactions after the cyst became sclerosis were analyzed.Logistic regression analysis was used to analyze the factors affecting the postoperative efficacy.Results In all the 5 groups,the suctioned fluid was dark red in colour,and the patients had cystic nodules.The preoperative mean cyst volume was(20.43±5.86)cm3.In all the 5 groups,the postoperative changes in cyst volume indicated that the postoperative one-month cyst volume significantly shrank when compared with the preoperative volume,the postoperative 3-month cyst volume remarkably shrank when compared with the postoperative one-month volume,and the postoperative 6-month cyst volume strikingly shrank when compared with the postoperative 3-month volume(all P＜0.05),while no statistically significant difference in the cyst volume existed between the postoperative 12-month value and the postoperative 6-month value(P＞0.05).The postoperative 6-month total effective rate of all the five groups was 87%(174/200),and no statistically significant differences in the postoperative 6-month curative effect existed between each other among the 5 groups(P＞0.05).Taking the postoperative 6-month curative effect as the dependent variable,and the age,sex,thick cystic wall,cystic septum,and preoperative cyst volume as independent variables,the binary logistic regression analysis was conducted,which revealed that the thick cystic wall(OR=0.24,95%CI=0.08-0.72,P=0.01)and the cystic septum(OR=0.21,95%CI=0.07-0.67,P=0.01)were the factors affecting the postoperative 6-month curative effect.The main side reaction was pain,which was tolerable by patients.There was no significant difference in the incidence of adverse reactions between each other among the five groups(all P＞0.05).Conclusion In treating thyroid cysts by using ultrasound-guided lauromacrogol sclerotherapy,there is no relationship between the curative effect and the percentage of the retained lauromacrogol dosage to the total cystic fluid.The best curative effect can be achieved at 6 months after injection of lauromacrogol,which can be used as the optimal time for follow-up check.The thick cystic wall and the cystic septum are the main factors that affect the curative effect of lauromacrogol sclerotherapy.For the treatment of thyroid cyst,lauromacrogol sclerotherapy carries reliable curative effect with few adverse reactions,therefore,this therapy is worthy of clinical application.(J Intervent Radiol,2024,32:69-73)