Types and chemical composition of intrahepatic stones.

The calcium bilirubinate stone is the typical gallstone found in patients with hepatolithiasis; a series of studies on the formation of stones have been performed by Maki [1966, 1982]. Results of chemical analysis and clinical factors lend support to Maki's bacterial beta-glucuronidase theory [Maki, 1966]. However, besides calcium bilirubinate these stones also contain other components such as fatty acids and free bile acids. The presence of these components indicates bacterial involvement, which is proved by the decomposition of the lecithine in bile to fatty acids by phospholipase A and the formation of free bile acids by deconjugation of the conjugated bile acids. In the formation of calcium bilirubinate stones, it is believed that diet [Matsushiro et al, 1977] and bacterial infections accompanying biliary stasis are important inducing elements. Since these stones are formed mainly in the bile ducts and recurrence rates are likely to be high, it is important from the therapeutic viewpoint to remove these inducing factors. However, it is still uncertain whether bacterial infection accompanying biliary stasis should be considered as an inducing factor in the development of fatty acid-calcium stones. More than 90% of all cholesterol and black stones are found in the gallbladder. However, when these stones are found in the intrahepatic bile ducts, it is still not clear whether they are expelled from the gallbladder or formed initially in the intrahepatic bile ducts. In patients who have cholesterol stones filling the entire biliary tract, it is difficult to conceive that these gallstones are first expelled from the gallbladder. In addition, in patients with black stones, the stones are located only in the dilated bile ducts, and stenosis of the bile duct is often recognized in the excisional stump of the liver at lateral segmentectomy. In these cases, the expulsion of stones from the gallbladder seems rather improbable. Different types of gallstones show a tendency to occur in certain regions; however, gallstones may be formed in almost any part of the biliary system if conditions are favorable. It can be concluded that the pathogenesis of hepatolithiasis may not be clarified only by analysis of the intrahepatic gallstones. In addition, an understanding of the formation of different types of gallstones may contribute to elucidation of the pathogenesis of hepatolithiasis.