Assessment of liver histology following orthotopic liver transplantation is an essential component of management in the transplant recipient. Most programs recommend liver biopsies when there are changes in the patient's status or biochemical tests. The use of protocol allograft biopsies, that is in asymptomatic recipients with normal or near-normal liver tests, is controversial. Considerations such as potential morbidity and mortality, cost, inconvenience, use of resources, and potential

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... of unexplained histopathological findings should be weighed against potential individual and societal benefits. More than one insult can contribute to late posttransplantation dysfunction and immunosuppression can influence the histological findings and the severity of many disease such as recurrent viral hepatitis, autoimmune hepatitis (AIH), and rejection. Histological analysis can help to determine the main component of injury, but careful clinicopathological correlation is needed. Biopsy interpretation should include an assessment of adequacy of the sample, and more than 6 portal tracts are considered adequate, a systematic examination, and a correlation with clinical aspects such as the original disease, immunosuppression, liver tests, viral serology, immunology and radiologic findings. Many transplant units follow centerspecific criteria; however, a wide use of the standardized criteria (Anonymous, 1997; Demetris 2000) would enable centers to compare and pool results, improve management, and better understand the pathophysiology of disease mechanisms. Early post-transplant period Of the many causes of graft dysfunction in the early posttransplantation period, acute allograft rejection, preservation or reperfusion injury, drug-induced liver injury, viral infection and bile duct injury are the most common, and a liver biopsy may be required for their specific diagnosis and optimal management. The histological changes of preservation/reperfusion injury are uncommonly severe and typically resolve during the immediate and early posttransplant period. Acute cellular rejection (ACR) normally occurs within the first month of transplantation and liver biopsy represents a valuable tool for its diagnosis and guiding treatment. Though the histological diagnosis is often straightforward, several clinical situations can pose diagnostic challenges, such as patients with co-exiting viral hepatitis and other forms of tissue injury. In the early postoperative period, transplant recipients receive many drugs that are potentially hepatotoxic, such as antibiotics, analgesics, immunosuppressive agents and total parenteral nutrition. Although the histological features of drug-induced liver injury are rarely diagnostic, recognition of drugwww.intechopen.com