The crystalline structure of pancreatic calculi.

The present study was carried out to investigate the ultrastructure and composition of crystals of pancreatic calculi. Microradiography showed that they were irregularly mineralized with radial or stratified zones of low mineralization. The crystals were identified as calcite composed of CaCO3 in X-ray and electron diffraction studies. Scanning electron microscopy (SEM) revealed that the calculi consist of aggregations of rhombohedral, fang-shaped, botryoidal, foliaceous, and plate-shaped crystals. Some of them showed signs of partial dissolution on their surface. Transmission electron microscopy (TEM) showed crystals of various sizes and shapes either solitary or in clumps. The direct measurement of crystalline lattice intervals obtained from each crystal was 0.386 nm in accordance with the diffraction data. Exocrine pancreatic cell debris are present in pancreatic calculus matrices.