Onion skin fibrosis of the common bile duct is

Refer Robbins page no Pg 860 MORPHOLOGY Morphologic changes differ between the large ducts (intrahe- patic and extrahepatic) and the smaller intrahepatic ducts. Large duct inflammation is similar to that seen in ulcerative colitis: acute, neutrophilic infiltration of the epithelium superim- posed on a chronic inflammatory background. Inflamed areas develop strictures because edema and inflammation narrows the lumen or because of subsequent scarring. The smaller ducts, however, often have little inflammation and show a strik- ing circumferential "onion skin" fibrosis around an increas- ingly atrophic duct lumen (Fig. 18-39), eventually leading to obliteration by a "tombstone" scar. Because the likelihood of sampling smaller duct lesions on a random needle biopsy is miniscule, diagnosis depends on radiologic imaging of the extrahepatic and larger intrahepatic ducts. As the disease pro- gresses the liver becomes markedly cholestatic, culminating in biliary cirrhosis much like that seen with chronic obstruction and primary biliary cirrhosis. Biliary intraepithelial neoplasia may develop and cholangiocarcinoma appears usually with a fatal outcomes.