Supradiaphragmatic accessory lobe of the liver in BB Wistar rats

Supradiaphragmatic accessory livers were observed in two closely related rats in a series of 172 necropsies on BB Wistar rats. The gross and histological appearance of both accessory lobes are described. This abnormality has been reported in only one other inbred strain of rats where it also arose with a very low incidence. As in the previous report, the pattern of occurrence of these accessory lobes suggests a mode of inheritance that is either polygenic or autosomal recessive with low penetrance.