Visibility of the graft hepatic artery using superb microvascular imaging in liver transplantation recipients: initial experience

Background: Hepatic artery (HA) obstruction is one of the most threatening complications following liver transplantation (LT); however, conventional color Doppler imaging (CDI) suffers from technical limitations regarding the visualization of fine vessels and low-velocity blood flow. Purpose: To test the visibility of HA in postoperative evaluation of LT using a superb microvascular imaging (SMI). Material and Methods: This retrospective study was approved by our institutional review board. Fifty-five consecutive patients (58 grafts; mean age = 56 years) who underwent LT with Doppler ultrasonography (US) on postoperative day 1 were included. We compared the subjective visibility of HA and objective measurements of HA caliber, visible HA length on CDI, monochrome SMI (mSMI), contrast-enhanced mSMI (CE-mSMI), and contrast harmonic imaging (CHI). Reproducibility of HA caliber measurements on SMI techniques were also evaluated by using intraclass correlation coefficients (ICCs). Results: The subjective image quality for visibility of HA tended to be graded higher with mSMI than CDI, and with CE-mSMI than mSMI (P < 0.001). The overall reproducibility of HA caliber measurements was good to excellent for both mSMI and CE-mSMI (ICC = 0.674-0.855). HA caliber measurements on mSMI and CE-mSMI strongly correlated with CHI (R = 0.785, 0.798, P < 0.001), while mean HA length on mSMI was significantly longer than on CDI (1.88 +/- 0.83 vs. 1.42 +/- 1.01 cm, P = 0.004), and even longer on CE-mSMI (vs. 3.28 +/- 1.11 cm, P < 0.001). Conclusion: The mSMI technique shows good reproducibility and correlates well with currently used methods for postoperative evaluation of HA in LT recipients. It is further improved by administration of an US contrast agent.