Microstructure of decalcified human calcium oxalate urinary stones

Human urinary stone fragments and sections were decalcified in ethylenediaminetetraacetic acid solution after embedding in 1% agar. These decalcified embedded stone specimens were then processed for scanning electron microscopy. After critical point drying the agar was removed and EDTA-insoluble stone residue was studied by scanning electron microscopy. This residue representing part of the stone matrix kept the original shape of the stone and was basically made of fibrous material. The fibers appeared to be arranged in matted sheets that were present as concentric laminations. In case of calcium oxalate dihydrate stones these fibrous sheets were also arranged as peripheral layers running parallel to the pyramidal faces of large calcium oxalate dihydrate crystals. In decalcified stones, crystals were represented by crystal ghosts. Often some vesicular material was present embedded in the fibrous sheets.