Pathology and biopsy diagnosis of the transplanted liver

Over the past 30 years, liver transplantation has evolved from an experimental therapy to a routine procedure and most pathology textbooks have now a section dedicated to the pathology of liver transplant. Although there remain problems of biopsy interpretation due to the numerous post-transplant complications which can occur singly or in association, the major changes have been well characterized and are reviewed here, a particular attention being given to those features which are unique to or distinctive of the liver allograft. These include the outcome of donor fatty liver, reperfusion damage, massive haemorrhagic necrosis and the patterns of rejections, in particular the rarity and delayed onset of hyperacute rejection and the selective involvement of the small interlobular bile ducts and vascular endothelia in both acute and chronic graft rejection. "Functional" cholestasis with hepatocyte ballooning, cholangiolar cholestasis associated with sepsis and lesions of the larger bile ducts which may result from preservation, immune and/or ischaemic injury and closely resemble the changes observed in primary sclerosing cholangitis are also considered. Later in the post-transplant course, changes due to de novo or recurrent hepatitis have to be distinguished from those of late cellular rejection, protracted biliary complications, lymphoproliferative disorders, disease recurrence, in particular autoimmune chronic hepatitis, primary biliary cirrhosis and sclerosing cholangitis, differential diagnoses which often require interpretation of allograft changes in conjunction with all laboratory and clinical data available.