To evaluate the value of ultrasound and contrast-enhanced ultrasound (CEUS) in the diagnosis of renal cell carcinoma with tumor thrombus in the inferior vena cava (IVC).

A retrospective analysis was performed on 113 patients with renal cell carcinoma complicated with tumor thrombus in the IVC who underwent surgical treatment at the Peking University Third Hospital from January 2015 to May 2018. All patients were examined by IVC ultrasound before operation, and 22 patients in whom tumor thrombus or thrombus could not be confirmed underwent CEUS examination. Postoperative pathological results were obtained in all patients. According to the postoperative pathology, the patients were divided into either a thrombosis group (n=27) or a non-thrombosis group (n=86). The clinical data and pathological and ultrasonic characteristics of the two groups were compared. The ROC curves of different parameters to evaluate thrombosis were drawn, and the area under the curve (AUC) was calculated. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of CEUS in the diagnosis of IVC tumor thrombus complicated with thrombosis were calculated by the four-fold table method.

In univariate analysis, the Mayo grade of tumor thrombus was higher (P=0.011), the maximum long diameter of tumor was smaller [(7.42±2.87) cm vs (9.37±2.88) cm, P=0.013], and the tumor thrombus was wider [(25.82±13.79) mm vs (19.79±10.73) mm, P=0.019] in the thrombosis group than in the non-thrombosis group. There were more patients without blood flow signal in the residual lumen [(19/27, 70.4%) vs (37/86, 43.0%), P=0.016] and more cases without anechoic necrosis in renal tumors [(17/27, 63.0%) vs (34/86, 39.5%), P=0.046] in the thrombosis group. The anteroposterior diameter of renal vein entrance of tumor thrombus was larger [(26.90±8.12) mm vs (20.59±6.87) mm, P<0.001] and the proportion of patients with segmental resection of the IVC was higher [(12/27, 44.4%) vs (9/86, 10.5%), P<0.001] in the thrombosis group. The ROC curve of the maximum long diameter of tumor was drawn; the AUC was 0.668 (P=0.006), and the best cut-off value was < 6.90 cm. The AUC of thrombus width was 0.669 (P=0.016), and the best cut-off value was>24.6 mm. The AUC of the anteroposterior diameter of the renal vein of tumor thrombus flowing into the IVC was 0.766 (P<0.001), and the best cut-off value was>23.6 mm. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of CEUS in the diagnosis of IVC tumor thrombus complicated with thrombosis were 71.4%, 93.3%,86.4%, 83.3% and 87.5%, respectively.

The smaller the tumor and the wider the tumor thrombus, the more likely a thrombus is formed. CEUS can improve the diagnostic efficiency for IVC tumor thrombus complicated with thrombosis, but only according to whether the thrombus is enhanced, there may be a deviation in the identification of bland thrombus and tumor thrombus.