Pathologically induced alterations in the dimensions of the hepatic portal vasculature of mice infected with Schistosoma mansoni

SUMMARY Alterations in the hepatic portal vasculature of NMRI mice infected with Schistosoma mansoni were assessed using a microsphere injection technique. The accumulation of eggs in the livers of infected mice and the development of portal hypertension were closely related to the worm pair burden during the first 15 weeks of infection. Individual variation between mice harbouring identical patent worm pair burdens was partially explained by the reduced fecundity of females from sexually biased infections. As eggs accumulated in the liver and portal hypertension increased, the number of injected microspheres escaping from the hepatic portal system rose in rank order of diameter from 9 μm through 15 μm and 25 μm to 50 μm. There was a strong correlation between the numbers of parasite eggs in the lungs and injected microspheres recovered from the lungs. The pattern of detection of microspheres in the lungs indicated a progressive increase in diameter of intra-hepatic porta-systemic connexions, followed by development of large-bore extra-hepatic collateral vessels. An accurate temporal profile of the pathological state of the host and the extent of collateral vessel formation was obtained. Injection of 141Ce-labelled microspheres demonstrated that the arterial supply to all organs of the body was affected by alterations in the micro-vasculature of the liver and lungs.