Acute and chronic hepatic allograft rejection: Pathology and classification

Hepatic allograft rejection has been divided into humoral (or hyperacute), acute (or cellular), and chronic (or ductopenic) forms. Humoral rejection i s extremely uncommon in the liver and is not graded. Acute rejection will o ccur in approximately 50% of liver allografts, is more common in the first few weeks posttransplantation, and is defined by Snover's triad of portal h epatitis, endothelialitis (or endotheliitis), and lymphocytic cholangitis. This form of rejection is generally reversible, either spontaneously or wit h additional immunosuppressive therapy, and can be reliably graded using a system with categories of mild, moderate, and severe rejection, associated with 37%, 48%, and 75% unfavorable shortterm and 1%, 12%, and 14% unfavorab le longterm outcomes, respectively. Chronic rejection is characterized hist ologically by progressive duct loss and a lipid-rich vasculopathy that can be difficult to diagnose in early phases. Chronic rejection typically occur s several months to a year posttransplantation, although exceptions exist. Copyright (C) 1999 by the American Association for the Study of Liver Disea ses.