Application of contrast-enhanced ultrasound before inferior vena cava filter recovery

BACKGROUND: This study aims to investigate the clinical value of contrast-enhanced ultrasound (CEU) before temporary inferior vena cava filter (IVCF) recovery in patients with deep venous thrombosis, in order to provide ultrasound signs for the recovery of IVCF in clinical practice. METHODS: The CEU manifestations of patients with deep vein thrombosis before temporary IVCF recovery were retrospectively analyzed. With the manifestations of digital subtraction angiography (DSA) or results of the surgical recovery of IVCF as the standard, the detection rate of a thrombus in IVCF was compared between conventional ultrasound and CEU, and the role of CEU in detecting complications of IVCF was analyzed. RESULTS: In the 103 patients with IVCF, conventional ultrasound and CEU did not reveal any filter displacement and deformation, as well as infection. In 86 patients, filters were successfully recovered under DSA. In one patient, the filter was removed surgically. In 16 patients, recovery failed or was given up, and inferior vena cava (IVC) angiography was performed. The recovery rate of IVCF was 84.5%. Among all cases, thrombi were found within the filters or around the filter in 23 patients. The detection rate of thrombi was 47.8% (11/23) by conventional ultrasound and 82.6% (19/23) by CEU, and the difference between these two methods was statistically significant (P<0.05). CEU drew a misdiagnosis of thrombus within the filter in one patient, and the diagnosis was not confirmed after the recovery of the filter. The diagnostic coincidence rate of CEU for thrombus in the IVCF was 95.1%, and the positive predictive value was 95%. In another case, the foot of the IVCF pierced out of the wall of the IVC into the intestinal wall; and this was confirmed by DSA. Hence, recovery was given up. CONCLUSIONS: Thrombosis is the main complication after IVCF placement. CEU revealed typical manifestations of thrombi in the IVC, and has overcome the shortcoming of color Doppler ultrasound such as angular dependence. Its detection rate of thrombi within the IVCF was higher compared with conventional ultrasound. Hence, this method can serve as a simple and accurate method for evaluating whether IVCF is suitable for recovery. This study provides a reliable imaging basis for the clinical selection of the means and time of IVCF recovery, reducing unnecessary intervention procedure.