Sclerosing cholangitis epidemiology and etiology.

Sclerosing cholangitis represents a spectrum of chronic biliary diseases that either has an unknown etiology (i.e., primary) or is caused by identifiable insults to the biliary tree (i.e., secondary). To date, the epidemiology of primary sclerosing cholangitis has been appraised; however, its etiology continues to be unclear. In contrast, the etiology of secondary sclerosing cholangitis is always known, but the epidemiology of this clinical entity is difficult to study.