Objective To observe the intimal changes of inferior caval vein(ICV) wall after combined thrombolysis and anticoagulation therapy for acute thrombosis in rats.Methods The inferior caval venous thrombosis model was established in 105 rats and they were randomly diride into 3 treated groups:heparin(A) treatment group(n=35),urokinase(B) treatment group(n=35),and combination of urokinase and heparin(C) treatment group(n=35),and also eslablished a sham(D) group(n=30).The thrombosed caval veins were taken 1,4,7,14,and 28 d after thrombosis.Changes of thrombus structure and orgainization and intimal hyperplasia were observed by light microscope.The expression areas of collagen fiber were measured by histochemistry.Scanning electron microscopy was used to observe the damage of endothelial cells.Results The intimal hyperplasia in A group was the most severe.The expression area of collagen fiber in group C was less than that of A and B groups(P