Assessment of drainage vein of focal nodular hyperplasia using contrast-enhanced ultrasound

Purpose: Identification of drainage vessels is useful for differential diagnosis of hepatic tumors. Direct drainage to the hepatic vein has been reported to occur in focal nodular hyperplasia (FNH), but studies evaluating the drainage veins of FNH are limited. We aimed to investigate the detection rate of the FNH drainage vein and the factors related to visualization of the drainage vein on contrast-enhanced ultrasound (CEUS). Methods: Fifty consecutive patients with 50 FNH lesions were retrospectively evaluated in this study. We calculated and compared the detection rate of the FNH drainage vein on CEUS, contrast-enhanced magnetic resonance imaging (CEMRI), and contrast-enhanced computed tomography (CECT), and identified the factors correlated with visualization of the FNH drainage vein on CEUS by using multivariate logistic regression analyses. Results: Visualization of the drainage vein was confirmed in 31 of 50 lesions (62%) using CEUS, three of 44 lesions (6.8%) using CEMRI, and one of 18 lesions (5.6%) using CECT. The detection rate of the FNH drainage vein on CEUS was significantly higher than that on CEMRI and CECT (p < 0.001). Multivariate analysis identified lesion size (≥ 25 mm) and detection of the spoke-wheel pattern on Doppler US as independent factors for drainage vein detection in FNH. Conclusion: Our study showed that rapid FNH drainage to the hepatic vein was observed at a relatively high rate on CEUS, suggesting that CEUS focusing on detection of drainage veins is important for diagnosing FNH.