The pathology of primary biliary cirrhosis and autoimmune cholangitis.

Primary biliary cirrhosis is the prototype of the small-duct biliary diseases which are characterized by damage or destruction of interlobular and proximal septal bile ducts. Autoimmune cholangitis differs serologically from primary biliary cirrhosis but, by current consensus, has the same pathological features. The histological findings in primary biliary cirrhosis and the staging criteria of that disease are well described and at this point can be applied to autoimmune cholangitis also. Diagnostic difficulties arise either because other small-duct biliary diseases are not considered or because tell-tale histological signs, particularly ductopenia, are not recognized. Review of all small-duct biliary diseases suggests that interlobular and adjacent septal bile ducts (1st and 2nd generation ducts) represent an immunosensitive portion of the biliary tree. Comparative studies of these unique segments may have important implications for our understanding of primary biliary cirrhosis and autoimmune cholangitis and possibly for future treatment options for these conditions.