[The mechanism of distant metastases of alveolar hydatid disease]

The mechanism of the distant metastasis of echinococcosis was investigated using jirds (Meriones unguiculatus) by inoculation of fractions obtained from echinococcal lesions formed in the peritoneal cavity of cotton rats (Sigmoid hispidus). Protoscoleces, cysts, and germinal cells were fractionated from the peritoneal lesions of the cotton rats injected peritoneally with echinococcal germinal cells. Each fraction (protoscoleces; 500 pieces, cysts; 50 pieces, germinal cells; 2 x 10(7) cells) suspended in 0.2 ml of PBS was injected into either the left inguinal vein (IV group) or the mesenteric vein (MV group) of seven week-old jirds. Eight weeks after the injection, the jirds were sacrificed and examined macroscopically and microscopically. In IV group, one of 10 jirds had echinococcal lesions in lung, bilateral adrenal, brain, para-aortic lymph node and left inguinal lymph node by inoculation of only germinal cells. Another one had lung lesions formed by cysts inoculated. In MV group, both intrahepatic and pulmonary echinococcal lesions by inoculation of germinal cells were observed in 3 out of 5 jirds. Cysts inoculated formed intrahepatic lesions in all 5 jirds. However, protoscoleces inoculated through both routes never formed echinococcal lesions in any organs. The typical lesions of echinococcosis were observed in all lesions without protoscoleces and calcification. These results indicate that germinal cells in intrahepatic echinococcal lesions might invade into the intrahepatic vein and metastasize to other organs.