Ultrastructure and elemental composition of human pancreatic calculi.

Scanning electron microscopy (SEM) and energy dispersive x-ray fluorescence (EDXRF) have been used in this study to investigate the morphology, nature, and arrangement of major, minor, and trace elements in human pancreatic calculi (PC) obtained from patients with alcoholic and tropical pancreatitis. The present study has confirmed previous observations that PC are rich in CaCO3 (as calcite) and many other elements. Further, we have shown for the first time that the amorphous nidus contained only iron, chromium, and nickel, whereas the outer shell contained calcium and 17 other elements. Based on our studies, we postulate the formation of PC to be taking place in multilayers and multistages. Formation of inner protein nidus in the form of a cobweb is the first stage, then calcite is deposited on this fibrous network as tiny crystals. Because of their high surface area and high surface activity, other metallic ions are incorporated onto it through co-precipitation, adsorption, and/or lattice substitution. This study has further shown that irrespective of the etiology for chronic pancreatitis, the structure and composition of PC are the same suggesting a common pathway for lithogenesis in the pancreatic duct.