Congenital venous hypoplasia in the liver of rats.

Narrowed and rudimentary portal vein branches were observed in the livers of specified-pathogen-free rats which, at the age of 6-11 weeks, showed poor condition and reatrded growth. At autopsy abdominal venous distension and congestion suggestive of portal hypertension and collateral circulation appeared to have developed. The cause of the observations and their significance in view of the use of the rats are unknown.