Objective:To evaluate the ultrasound diagnostic value of portal vein complications after liver transplantation by monitoring changes in portal vein hemodynamic parameters using the color Doppler ultrasound technology and to determine its clinical significance.Methods:The clinical data of 99 patients who underwent liver transplantation at the Organ Transplantation Center of the Affiliated Hospital of Qingdao University from July 2015 to December 2018 were analyzed retrospectively. There were 81 males and 18 females, aged (51±9) years old. These patients were divided into the portal vein complication ( n=23) and the non-portal vein complication ( n=76) groups, based on whether portal vein complications had developed within 2 years after surgery. In addition, 30 healthy volunteers at the Affiliated Hospital of Qingdao University, including 16 males and 14 females, aged (40±14) years old were selected to form the control group. The patients’ morphology of liver was studied using color Doppler ultrasound at days 1, 7, 14, 30, 180, 365 and 730 after liver transplantation, and the maximum portal vein blood flow velocity and portal blood flow were recorded. Results:Compared with the control group, the maximum portal venous flow velocity and portal venous blood flow significantly increased on days 1, 7, 14, 30, and 180 after liver transplantation in the non-portal complication group (all P<0.05). With time, these changes showed a decreasing trend. By day 365 after surgery, the differences between the maximum portal venous flow velocity and the portal venous blood flow between the two groups became not significant ( P>0.05). Of the 23 patients in the portal vein complication group, 9 developed portal vein stenosis (PVS) and 14 portal vein embolism. The 9 patients with PVS had a maximum portal flow velocity of 63.8 (46.0, 78.6) cm/s at 1 month after surgery, and this flow velocity was significantly higher than that in the non-portal complication group [35.0(29.6, 41.8) cm/s, Z=-3.35, P<0.001]. The portal blood flow was 993 (887, 1168) ml/min in the 9 patients with portal vein stenosis at 1 month after surgery, and it was significantly higher than those in the non-portal complication group [811(682, 1 018) ml/min, Z=-2.37, P=0.020]. Conclusions:After liver transplantation, both the portal venous blood flow velocity and the blood flow were at high levels in the early postoperative period and they returned to normal levels with time. Ultrasound dynamic monitoring of portal venous blood flow changes was of clinical significance in diagnosing portal vein stenosis and portal vein embolism after liver transplantation.