Liver capsule thickening characterized by mesothelial cell proliferation with vascularization in broilers ascites syndrome

Abstract

Thickened liver serosal membranes in 24 8-week-old male young broiler chickens with the ascitic syndrome were pathologically examined. Gross changes included inflammation of liver capsules (15/24 cases), right ventricular dilation (24/24 cases), pericarditis (5/24 cases), peritonitis (9/24 cases) and air sacculitis (7/24 cases). Histopathology revealed liver capsule thickening and focal hepatitis in all 24 cases, peri- and epi-carditis in 19 and myocarditis 11 cases. The thickened liver capsules consisted of spindle shaped-cells which reacted with anti-keratin rabbit serum and anti-vimentin monoclonal antibody, and formed cysts of varying size containing clear yellow fluid as ascitic fluid. The volume of sub-capsular fluid may have been responsible for the development of the cysts. The spindle-shaped cells were located perpendicular to the surface with thin bridges from the serosa together with a little collagen and vascularization. These changes were not observed in other serosal membranes in abdominal air sac or pericardium. We have therefore shown that the liver capsule thickening in the broilers ascites syndrome is characterized by mesothelial cell proliferation with vascularization.