Collaterals through hepatic sinusoids after embolization of terminal portal venules: an in vivo study on mice

The changes of intrahepatic microcirculation during the very early stage of portal venule obstruction are not well known. The aim of this study was to clarify the immediate alterations of intrahepatic microcirculation after selective obstruction of the terminal portal venules in vivo. After selective embolization of terminal portal venules with plastic beads whose diameter was 30-35 μm, the hepatic microcirculation of 136 embolized areas on 15 mice was observed with epi-illuminated in vivo fluorescent microscopy. There was reverse blood flow in sinusoids resulting in three types of collaterals after embolization of the terminal portal venules. These collaterals were derived from the proximal trunk of the embolized terminal portal venules, adjacent branches and neighboring terminal portal venules, and they could appear simultaneously with a frequency of 59/136 (43.4%), 77/136 (56.6%) and 131/136 (96.3%), respectively. Collateral formation was strongly correlated with the state of blood flow in the surrounding area (P < 0.0001), but not with the extent of the embolized areas. The results indicated that after embolization of terminal portal venules, reverse blood flow occurred in sinusoids to form collaterals, and these collaterals could maintain the microcirculation of the embolized area.