Perfusion of colorectal hepatic metastases. Relative distribution of flow from the hepatic artery and portal vein

Abstract

The importance of portal circulation in the delivery of drugs and nutrients to colorectal hepatic metastases is controversial. Using ¹³N (nitrogen 13) amino acids and ammonia with dynamic gamma camera imaging, we demonstrate, for the first time in human beings, a quantitative advantage of hepatic artery compared with portal vein infusion. Eleven patients were studied by hepatic artery injection, five patients were studied by portal vein injection, and two patients had injections through both routes. Data collected from the liver for 10 minutes after rapid bolus injection of ¹³N L-glutamate, L-glutamine, or ammonia were compared with ^99mTc (technetium) macroaggregated albumin (MAA) images produced after injection through the hepatic artery or portal vein at the same session. Tumor regions defined from ^99mTc sulfur colloid scans were compared with nearby liver areas of similar thickness. For the ¹³N compounds, the area-normalized count rate at first pass maximum (Qmax) and the tissue extraction efficiency were computed. The tumor/liver Qmax ratios for MAA and ¹³N compounds were highly correlated. Both tumor and liver extracted more than 70% of the nitrogenous compounds. The tumor/liver Qmax ratios reflect the relative delivery of injected tracer per unit volume of tissue. After hepatic artery injection the Qmax ratio was 1.03 ± 0.33 (mean ± SD), significantly exceeding the Qmax ratio of 0.50 ± 0.34 after portal vein injection (P < 0.003). Therefore, (1) more than twice as much of a nutrient substrate is delivered per volume of tumor relative to liver by the hepatic artery as by the portal vein; (2) the high extraction efficiency demonstrates that the hepatic artery flow is nutritive; and (3) the delivery of substance in solution (such as nutrients or drugs) to tumor and liver tissue correlates with the distribution of colloids such as macroaggregated albumin after hepatic arterial and portal venous injection.