Measurement of portal-systemic shunting in the rat by using gamma-labeled microspheres

A method for determining the extent of portal-systemic shunting (PSS) is described and evaluated in lightly anesthetized (ketamine) rats. This method relies on the intrasplenic injection of 15-micrometers gamma-labeled spheres and the subsequent measurement of liver and lung radioactivities. After the splenic injection of the microspheres, a fraction of microspheres shunting the hepatic sinusoidal bed will be entrapped in the lungs. Thus, the ratio, lung/(lung + liver) radioactivities, will indicate the degree of PSS. The percent of PSS was determined in normal (n = 13; 1.2 +/- 0.3%), in cirrhotic (n = 9; 15.0 +/- 4.5%; P less than 0.01), and in portal vein-ligated animals (n = 14; 95.0 +/- 0.9%; P less than 0.001 for normal and cirrhotic). In addition, PSS was sequentially quantitated (n = 3) before (3.0%) and after (89%) partial portal vein ligation. The variability of PSS found in cirrhotic rats (0.7-41.0%) is in agreement with the reported data for PSS in patients. This technique, which is simple, rapid, and reproducible, allows the quantitation of PSS in small laboratory animals.