The use of quantitative scintigraphy in the measurement of portal-systemic shunting in rats

Portal-systemic shunting was studied in 54 portal hypertensive rats bothin vivo andin vitro using radioactive microspheres. The animals underwent partial portal vein ligation around needles of varying diameter to produce a wide range of shunting. Two to four weeks later, quantitative lung-liver scintigraphic and whole body images were obtainedin vivo following ileocolic vein injection with99mTc-MAA. After sacrifice, the lung and liver activities were determined by the gamma camera, a dose calibrator, and a well counter. Portal-systemic shunting ranged from 0.1–97.6%. When shunting was comparedin vivo andin vitro, an excellent correlation was found (r=0.99, p< 0.001). A subgroup of 24 animals had consecutive injections of99mTc-MAA and51Cr-labeled 15 μm microspheres, which, although different in size, yielded similar results (r=0.89, p< 0.001). We conclude that in small laboratory animals a wide range of shunting can be measured accuratelyin vivo by quantitative scintigraphy.