Doppler ultrasound in prediction of the early mortality risk factors on the waiting list for pediatric liver transplantation recipients

Abstract

UE TO SHORTAGE of organ donation, limited manpower, and financial resources, a high mortality rate was found on the waiting list for pediatric liver transplantation. The purpose of this study was to document the variable changes in the hemodynamics of hepatic artery and portal vein by Doppler ultrasound and to assess their significance to the mortality in the waiting list and the need for early surgical intervention of liver transplantation for life-saving purposes. MATERIALS AND METHODS There were 36 pediatric patients included in this study (17 girls and 19 boys, age from 0.5 to 7.8 years old, mean age of 1.8 years) with underlying diseases of biliary atresia (29), glycogen storage disease (3), idiopathic portal hypertension (2), type I choledochal cyst (1), and liver hemangioendothelioma (1). We carried out monthly Doppler sonography examination on these potential recipients waiting for a liver transplant for the past 2 years to obtain progressive update data. Ultrasound examinations were performed by a single observer experienced in abdominal and Doppler techniques, using an Acuson 128XP10 (Acuson, Mountain View, Calif, USA) machine with a 3.5- to 7.0-MHz transducer available for color Doppler imaging. All the measurements of the portal veins were obtained at the extrahepatic portion of the main portal vein near the bifurcation. The portal flow direction was recorded as hepatopetal or hepatofugal. The angle-corrected flow velocity and cross-sectional area of the portal vein were obtained at the same site. The sample volume size for the Doppler scan was set at 1 to 3 mm, about half the diameter of the measured portal vein. This velocity was corrected by the angle (within 30 to 60 degrees) between the long axis of the portal vein and the Doppler beam. We calculated the portal flow volume per body weight as described by Kawasaki et al 1 The portal blood flow volume (PBFV) was calculated using the formula: PBFV 5 portal vein time average velocity (TAV) (cm/ s) 3 portal vein cross sectional area (A) (cm 2 ) 3 60/body weight (BW) (kg). Measurements of the hepatic artery including Doppler US waveform, peak systolic velocity (PSV), and resistance index (RI) were obtained along the hepatic hilum. The PSV of the hepatic artery was detected and corrected along the long axis of the color-coded hepatic artery. The angle between the long axis of the color-coded vessel and the Doppler beam was less than 30 degrees. The Doppler sample volume was set about 1 to 2 mm as half to the measured arterial caliber. The pulse repetition frequency was maintained at the lowest possible shift range to avoid aliasing. An average of three tracing of all the measurements obtained at the same site were used to generate a mean PSV and RI. The hepatic artery resistance index (HARI) was calculated automatically by the computer software of the ultrasound machine by the formula: HARI 5 (S 2 D)/S, where S is peak systolic velocity and D is end diastolic velocity. We divided the studied cases into two groups respectively by each of variable factors such as age, body weight, fever (septicemia), esophageal varices (E-V) bleeding, severe jaundice, amount of ascites, PBFV, and HARI, which may be significant as high risk factors of mortality. RESULTS Of the 36 children waiting for liver transplantation, all underwent Doppler ultrasound examination of preoperative evaluation for hepatic hemodynamics in the past 1 year. There were six cases of mortality in the 36 cases studied, and overall cumulative mortality rate in the past 1 year was 18%. There were 10 cases that received liver transplantation for life-saving reasons in subsequent time, and they were all alive; these cases were excluded for survival analysis, thus the mortality of the waiting list should be corrected. Therefore the mortality rate was 23% higher on these 26 cases of nontransplantation. ANALYSIS OF THE PREDICTIVE RISK FACTORS