In order to understand the effect of prednisolone injection on the histopathological changes of the mouse liver and the chronological changes of the worm structure of Clonorchis sinensis, when this fluke was inoculated to the mouse intraperitoneally. The recovery rate, survival rate, location and size of the inoculated worms as well as the histopathological changes of the liver were investigated for the comparison among the groups of mice, which were classified by number of worms and the duration of observation period. The result obtained were summarized as follows: The recovery rate and survival rate of the worms decreased especially 28 days after the inoculation. Most of worms (45.5 percent) were collected from the peritoneal cavity, and some of worms were found tightly adherent to the capsules of the liver, spleen, intestine and diaphragm. The mean worm size after inoculation was constantly smaller than that before inoculation. Remarkable atrophy in the reproductive organs of the worm, such as spermatheca, testes, vitelline gland and ovary was frequently observed at the 10th day of inoculation. Histopathologically the liver failed to show any parasitic worm inside the intrahepatic biliary system. However, multiple well formed egg-containing granulomas were present along the liver capsule. These necrotic granulomas were occasionally found under the fibrotic liver capsule. Focal necrosis and focal phlebitis together with vascular dilatation were prominent features of the liver. The worms recovered in the capsule of the liver were degenerated and necrotized. Usually, there were remarkable capsulitis and granuloma formation around the eggs.
