Histopathological and immunohistochemical investigations of hepatic lesions associated with congenital portosystemic shunt in dogs.

Canine livers with congenital portosystemic shunt were investigated histopathologically and immunohistochemically before and 8-272 days after partial ligation of the shunt. Lesions included hypoplasia of portal veins, arteriolar and ductular proliferation, lymphangiectasis, mild to moderate fibrosis, fatty cysts, and mostly mild hepatocellular damage with frequent atrophy and steatosis, regardless of the location of the shunting vessel. Perisinusoidal hepatic stellate cells (HSCs) in normal canine liver expressed alpha-smooth muscle actin (alpha-SMA), but no desmin. In altered livers, however, raised expression of alpha-SMA was detected, together with expression of desmin, in varying numbers of HSCs. This was interpreted as a sign of cellular proliferation and transformation to myofibroblast-like cells. Additionally, there was an obvious perisinusoidal increase of several extracellular matrix components. Postoperative biopsy samples showed basically the same lesions as those of pre-operative samples, except that signs of resolution of hepatic changes were apparent.