Quantitative assessment of hepatic function during liver regeneration in a standardized rat model

Reliable assessment of hepatic function during liver regeneration is crucial after liver surgery or liver transplantation. (99m)Tc-galactosyl human serum albumin ((99m)Tc-GSA) scintigraphy, (99m)Tc-mebrofenin hepatobiliary scintigraphy (HBS), the indocyanine green (ICG) clearance test, and the galactose elimination capacity (GEC) are common quantitative liver function tests. However, to our knowledge, comparative analysis between these tests has never been performed during liver regeneration. The aim of this study was therefore to compare (99m)Tc-GSA scintigraphy, (99m)Tc-mebrofenin HBS, the ICG clearance test, and GEC in the assessment of hepatic function during liver regeneration in rats. Rats were subjected to 70% partial hepatectomy (PHx). Liver function and functional volume were determined at predefined times after PHx and expressed as a percentage of baseline (pre-PHx) values. During liver regeneration, functional liver volume measured by (99m)Tc-GSA SPECT correlated strongly with conventional liver volume based on wet weight. One day after 70% PHx, conventional liver volume overestimated liver function as measured by (99m)Tc-mebrofenin uptake and excretion rates, (99m)Tc-GSA uptake rate, and ICG clearance. On days 5 and 7, (99m)Tc-mebrofenin uptake and ICG clearance had recovered to levels similar to conventional liver volume, whereas (99m)Tc-GSA uptake reflected a reduced liver function in relation to conventional liver volume and (99m)Tc-mebrofenin uptake. The GEC measurements consistently overestimated liver function during regeneration. Volumetric assessment of the liver should be complemented by liver function-specific assays. Functional regeneration is impaired, compared with volumetric regeneration, in the early phase of liver regeneration. In later stages of liver regeneration, (99m)Tc-GSA uptake underestimates hepatic regeneration in comparison to liver volume and (99m)Tc-mebrofenin uptake. GEC is of less value because it is only minimally affected by 70% PHx and is influenced by factors not related to liver function. (99m)Tc-mebrofenin HBS has the advantage of providing visual and quantitative information regarding both uptake and excretory liver function.