Abstract： Objective:To explore the value of quantitative parameters of enhanced MRI in predicting the establishment of inferior vena cava collateral circulation in patients with renal cell carcinoma and inferior vena cava tumor thrombus.Methods:Sixty-seven patients with renal cell carcinoma and inferior vena cava tumor thrombus who underwent radical resection and inferior vena cava venography in First Medical Center, PLA General Hospital from May 2006 to January 2021 were included retrospectively. According to the results of inferior vena cava venography, the patients were divided into two groups: the well-established collateral circulation group ( n=41) and the poor-established collateral circulation group ( n=26). Quantitative parameters were measured on preoperative enhanced MRI images, including tumor size, the maximum diameter of bilateral lumbar veins, the length of tumor thrombus, and the long and short diameters of tumor thrombus. Student′s t test or Mann-Whitney U test was used for comparison between the two groups. The independent risk factors related to the establishment of collateral circulation were obtained by binary logistic regression analysis and the model was established. The receiver operating characteristic curve was employed to evaluate MRI quantitative parameters and the logistic model, and the area under the curve (AUC) was compared by the DeLong test. Results:Between the well-established collateral circulation group and the poor-established collateral circulation group, the maximum diameter of the right lumbar vein, the maximum diameter of the left lumbar vein, the length of the tumor thrombus, the long diameter of the tumor thrombus, and the short diameter of the tumor thrombus were different significantly ( P<0.05). There was no significant difference in the tumor size between the two groups ( t=0.30, P=0.766). The AUC of the maximum diameters of the right lumbar veins and left lumbar veins, length of tumor thrombus, long and short diameters of tumor thrombus in predicting the collateral circulation were 0.917 (95%CI 0.824-0.971), 0.869 (95%CI 0.764-0.939), 0.756 (95%CI 0.636-0.853), 0.886 (95%CI 0.785-0.951), and 0.906 (95%CI 0.809-0.963). The AUC of the maximum diameter of the right lumbar vein and the short diameter of the tumor thrombus were larger than those of the length of the tumor thrombus, and the differences were statistically significant ( Z=2.25, 2.04, P=0.025, 0.041), but the AUC between other parameters had no significant difference ( P>0.05). The maximum diameter of the right lumbar vein (OR 24.210, 95%CI 2.845-205.998), the maximum diameter of the left lumbar vein (OR 20.973, 95%CI 2.359-186.490), and the length of the tumor thrombus (OR 23.006, 95%CI 2.952-179.309) were independent risk factors for predicting the establishment of inferior vena cava collateral circulation. The AUC of logistic model was 0.969 (95%CI 0.931-1.000). Conclusion:Quantitative parameters of tumor thrombus and lumbar vein based on enhanced MRI have a good ability in predicting the establishment of inferior vena cava collateral circulation in patients with renal cell carcinoma and inferior vena cava tumor thrombus. The maximum diameter of bilateral lumbar veins and the length of the tumor thrombus were independent risk factors for inferior vena cava collateral circulation.