Scanning electron microscope studies of human gallstones after plasma etching.

The morphological relationship between cholesterol and the calcium carbonate polymorphs and other inorganic constituents in intact human gallstones was investigated with scanning electron microscopy (SEM) after plasma etching the specimen instead of chemical dissolution of the organic constituents. The technique allowed magnification of more than 22,000x without structural damage or distortion. A framework of inorganic material that also contained crystals of calcium carbonate, vaterite, aragonite, calcite, and apatite remained after plasma etching. All cholesterol monohydrate and bile pigment compounds had been removed. The plasma etching technique allowed SEM studies of intact gallstones. An inorganic framework matrix was found in all stones. Its possible role in their formation is discussed.