Characterization of portal lymphocytic infiltrates in feline liver

To better understand the relationship of portal lymphocytic infiltrates to feline inflammatory liver disease, liver sections were semiquantitatively evaluated from healthy cat and liver sections randomly selected at necropsy from clinical cases. Healthy specific pathogen-free kittens and healthy young adult cats had up to 10 lymphocytes and plasma cells per portal area. Neutrophils were infrequently seen in portal areas. Approximately one-third of sections obtained from clinical cases younger than 10 years had increased numbers of lymphocytes and plasma cells in portal areas. Seventy percent of these had a concurrent increase in neutrophils. Eighty-two percent of liver sections obtained from clinical cases older than 10 years had increased numbers of portal lymphocytes and plasma cells. Almost all of these sections had concurrent fibrosis and bile duct proliferation. These data indicate that a progressive lymphocytic portal hepatitis is a common finding in cats older than 10 years.