PATHOGENESIS OF DUCTAL PLATE ABNORMALITIES

Intrahepatic bile ducts (IHBDs) develop from bipotential liver progeni tor cells in contact with the mesenchyme of the portal vein and thus f orm the ''ductal plates.'' The ductal plates are remodeled into mature tubular ducts, Lack of remodeling results in the persistence of perip ortal epithelial sleeves or ''ductal plate malformation'' (DPM). A pro posal is that virtually all congenital diseases of IHBDs represent exa mples of DPM. Some early, severe types of extrahepatic bile duct atres ia are characterized by DPM, a suggestion of a prenatal beginning of t he disease, Several congenital diseases are characterized by dilatatio n of segments of IHBDs and variable degrees of fibrosis, Such ''fibroc ystic diseases'' represent DPM at different levels of the biliary tree , Autosomal recessive polycystic kidney disease represents DPM of inte rlobular bile ducts, associated with tubular dilatation of collecting renal tubules, Congenital hepatic fibrosis may derive from the same ty pe of liver lesion, through a superimposed destructive type of cholang iopathy associated with scarring fibrosis, Caroli's disease represents DPM of the larger IHBDs, whereas Caroli's syndrome combines the lesio ns of Caroli's disease and congenital hepatic fibrosis, von Meyenburg complexes represent DPM of smaller interlobular ducts; their dilatatio n gives rise to the liver cysts in autosomal dominant polycystic kidne y disease, Finally, DPM is a component of the tissue abnormalities in so-called mesenchymal hamartoma.