Scanning electron microscopy in gallstone research.

Nidation of gallstones by inorganic or organic Ca salts was studied in 336 consecutive cases by SEM/EDXA and additional methods (X-radiography, X-diffraction, IR spectroscopy). SEM/EDXA proved to be a useful method in studying very small radio-dense nuclei, since common means of phase analysis are limited because of the small amounts of material to be analyzed. In 20.3% stones had radio-dense nuclei composed of either Ca-phosphate- and/or Ca-carbonate microcalculi. Ca-palmitate and/or pigments were at the centre of stones showing a less dense X-shadow. Nidation of cholesterol stones by defined pigment microcalculi was observed in 10 cases. Microstructures, for instance Ca-carbonate- and pigment microcalculi of identical structure to the central nidi, were found in corresponding bile sediments, confirming the role of such structures in gallstone nidation. Two structural features were identified in pigment stones: small, irregular granules, and glassy, poorly structured masses. Ca-bilirubinate calculi were built up from granules while the so called 'black' stones were composed entirely of the glassy masses or contained both structural elements, indicating that bilirubinate may be involved in the formation of some black stones, too. As revealed by EDXA and EPMA Ca was predominant in both subtypes while the black stones additionally contained Cu, Fe and, above all, considerable amounts of S. the latter was found to be in a low, non-SO4-valence state.