The use of hepatocyte extraction fraction to evaluate neonatal cholestasis

Purpose: Hepatobiliary scintigraphy is used routinely to evaluate infants w ith neonatal cholestasis. Hepatobiliary scintigraphy determines biliary pat ency by detecting radioactivity in the bower on imaging, in duodenal and ga stric aspirates, or all of these. During hepatobiliary scintigraphy, the he patocyte extraction fraction (HEF) is calculated by deconvolution analysis. Normal values of HEF are more than 90%. It is believed that HEF may predic t hepatic dysfunction, because, during hepatobiliary scintigraphy, the radi opharmaceutical used in this test is extracted by the hepatocytes from the blood stream. Therefore, a low value of HEF is seen with more severe hepato cellular disease. The goal of this study was to determine whether HEF has a ny correlation with synthetic liver function, whether HEF can differentiate obstructive from nonobstructive lesions that cause neonatal cholestasis, a nd whether HEF can predict the outcome of the different causes of neonatal cholestasis. Methods: A retrospective analysis of 68 hepatobiliary scintigraphy results was done in patients with neonatal cholestasis for a period covering 6 year s. Results: The HEF was available in 67 of these 68 patients, with a median va lue of 25% (range, 3.3% to 100%). The results of synthetic liver function t ests (i.e., albumin and prothrombin time) were normal in all infants with n eonatal cholestasis. No significant correlation was detected between HEF an d the serum levels of total and direct bilirubin, albumin, alkaline phospha tase, and prothrombin time by exploratory data analysis (R = 0.08; small, P > 0.2). The HEF values in different causes of neonatal cholestasis were co mpared: extrahepatic biliary atresia, neonatal hepatitis, and a miscellaneo us category consisting of alpha(1)-antitrypsin deficiency, ischemic hepatit is, paucity of bile ducts, and others. The outcomes of these diseases were assessed as resolution, continuing disease, transplantation, or death, but no predictive correlation was found with HEF. Conclusions: A single determination of HEF is of no value in assessing synt hetic liver function (as assessed by albumin and prothrombin time), specifi c diagnoses, and outcomes in patients with neonatal cholestasis. Therefore, a low isolated value of HEF should not be considered suggestive of poor pr ognosis and outcome in these patients.