Lipids of pigment gallstones

The lipids of pigment gallstones were analyzed. In contrast to previous reports, pigment stones were found to contain a wide variety of free fatty acids. In addition, pigment stones contained unhydrolyzed phospholipids. Both free fatty acids and phospholipids were present in much higher concentrations in a brown stone obtained from a patient with a biliary tract infection than in a black stone obtained from a patient with sterile bile and a long-standing hemolytic anemia. However, the phospholipids in both kinds of stone consisted primarily of phosphatidylcholine. Separation of stone and bile phosphatidylcholines into their individual molecular species by high performance liquid chromatography indicated that the phosphatidylcholines in stones closely resemble those in bile. The data suggest that both the free fatty acids and the phosphatidylcholine of pigment stones derive from bile phosphatidylcholine, but that the extent of bile phosphatidylcholine participation in pigment stone formation may be variable.