Background The pathogenesis of hypersplenism and the immune function of the spleen in patients with portal hypertension(PH)remain obscure.This study aimed to evaluate the morphological changes of blood spleen barrier in spleen with hypersplenism due to PH and provide evidence for an in-depth investigation of the immune function of the spleen with hypersplenism and the mechanism of hypersplenism.Methods Spleen samples from 12 portal hypertensive patients and 4 patients with traumatic ruptures of spleen were examined.The samples of spleen were made into pathological sections,stained with Masson trichrome stain,Gomori stain,and CD68,CD34 immunohistochemistry,and were examined microscopically for the changes in the distribution of collagen fibers,reticular fibers,macrophages,and vascular endothelial cells.The changes in ultrastructure of macrophages and endothelial cells in marginal zone were also evaluated by transmission electron microscopy.Results As compared to the normal spleen,the density of macrophage in the PH spleen was decreased,but the macrophages were mainly located in the marginal zone and distributed around the splenic corpuscle,with many villi and pseudopodium-like protrusion on the cell surface.The accrementition of collagen fibers was obvious around the splenic corpuscle and central artery.The increased reticulate fibers encircled the splenic corpuscle with more connection between the fibers.The vascular endothelial cells were in diffused distribution,without any regionality in PH spleen,but the vessel with enlarged lumina increased in red pulp.Conclusions The morphological changes of the blood spleen barrier can be one of the pathological fundaments for the abnormality of the immune function and the increased destruction of blood cells located in the spleens of patients with PH.However,this still entails clarification.