Morphological features of pathological membrane of inferior vena cava associated with Budd-Chiari syndrome

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Objective To investigate the morphological features of a diseased inferior vena cava (IVC) diaphragm associated with Budd-Chiari syndrome,and to explore the pathogenic mechanisms.Methods Ten patients with a diseased IVC diaphragm associated with Budd-Chiari syndrome underwent radical resection in our hospital frome October 2007 to December 2010.We assessed the gross morphological features of these diaphragms.The structure of the diseased diaphragms was compared with that of the IVC retrohepatic segment using light and electron microscopy.Results The diseased diaphragms were located within 2.0 cm from the junction of the IVC and the right atrium.The diaphragms had thick edges and relatively thin centers; their surface connected with the inner membrane of the IVC.A mural thrombus was observed in the IVC below the diaphragm in nine patients,with partial calcification of the diaphragm in five patients.Light microscopy revealed that the diaphragm was composed of massive homogencous collagen fibers and fibroblasts.The collagen was highly disorganized and some collagen fibers showed hyaline degeneration.The edges of the diaphragms showed proliferation of fibrous connective tissue,together with some pathological changes,including the presence of some granulation tissue and neovessels.The structures of the normal inner,middle and outer membranes of the IVC remained intact.Electron microscopy revealed the diaphragms contained a relatively high number of fibroeytes,and a small number of endotheliocytes on their surface.Most of the cristae inside the endotheliocytes were disconnected from the inner membranes and fused,and were therefore blurred or missing,The rough endoplasmic reticulum was also slightly dilated.Apoptotic cells were infrequent,and were generally smaller than expected.The endotheliocytes on the normal IVC walls were well organized,showing a striped distribution.Mitochondria,rough endoplasmic reticolum and pinocytotic vesicles were found inside the endotheliocytes.Collageo fibers and elastic fibers below the endotheliocytes were sparse.Conclusion The diseased IVC diaphragm associated with Budd Chiari syndrome mainly develops as a result of fibrocyte proliferation,although IVC injury and inflammatory reactions may also be involved. Key words: Budd-Chiari syndrome; Inferior vena cava; Pathological membrane