['To examine the relation between hepatic reticuloendothelial system (RES) dysfunction and the development of acute biliary pancreatitis. In an opossum model, the authors tested the hypothesis that RES blockade can turn the mild pancreatitis seen after pancreatic duct obstruction (PDO) into the severe form.', 'Biliary obstruction is considered the decisive event in gallstone pancreatitis. Suppression of the RES occurs during biliary obstruction.', 'Eighteen opossums were placed into three groups of six animals each: group A, RES blockade with lambda-carrageenan; group B, PDO; and group C, PDO and RES blockade with carrageenan. The severity of pancreatitis was evaluated by enzyme serum levels and percentage of pancreatic tissue necrosis. RES capacity was measured by dynamic liver scintigraphy, and hepatic blood flow was documented using the hydrogen clearance technique.', 'No changes in hepatic blood flow occurred in groups A to C. RES capacity was suppressed in groups A and C; in group B, RES function remained unchanged. In group A, amylase and lipase levels remained normal, 3 +/- 1.9% of pancreatic tissue were necrotic. The animals in group B developed mild edematous pancreatitis with an increase in amylase and lipase levels and 15 +/- 10% of pancreatic necrosis. In group C, amylase and lipase increased significantly and histology revealed severe necrotizing pancreatitis, with 72 +/- 11% of necrotic areas.'] Does reticuloendothelial system blockade promote progression from mild to severe acute pancreatitis in the opossum?