Kim K M, Johnson F B
Scan Electron Microsc. 1981(Pt 3):147-54.
Calcium oxalate stones are very common and increasing. Crystal growth is no less important than the crystal nucleation in the pathogenesis of stone formation. The crystal growth was studied in human calcium oxalate stones by a combined electron microscopy and x-ray diffraction. The main mode of weddellite growth was interpenetration twinning of tetrahedral bipyramids. Bipyramids may form as initial crystal seeds, develop from anhedral crystals (crystals which lack flat symmetric faces) of spherular or mulberry shape, develop on the surface of preformed bipyramids by spiral dislocation mechanisms, or develop on whewellite crystal by heterogeneous nucleation and epitaxy. Heterogeneous nucleations of whewellite on weddellite, and calcium apatite on whewellite were also observed. Whewellite grew mainly by parallel twinning. Interpenetration twinning was exceptional. Transformation of anhedral to euhedral (completely bounded by flat faces that are set ar fixed angles to one another) whewellite occurred by parallel fissurations followed by brick wall like stacking of the crystals, while euhedral transformation of weddellite occurred by protrusion of bipyramids frm anhedral crystal surface. Occasionally, an evidence of crystal dissolution was noted. Although an aggregation of crystals is believed to play a pivotal role in stone nidus formation, growth in size of the formed crystals, and twinning and epitactic crystal intergrowth apparently play a significant role in the obstructive urinary stone formation.
草酸钙结石非常常见且发病率不断上升。在结石形成的发病机制中，晶体生长与晶体成核同样重要。通过电子显微镜和X射线衍射相结合的方法，对人体草酸钙结石中的晶体生长进行了研究。水草酸钙的主要生长方式是四面双锥体的穿插孪晶。双锥体可能作为初始晶体种子形成，从球状或桑椹状的无定形晶体（缺乏平整对称面的晶体）发育而来，通过螺旋位错机制在预先形成的双锥体表面生长，或者通过异质成核和外延在二水草酸钙晶体上生长。还观察到了二水草酸钙在水草酸钙上以及磷酸钙在二水草酸钙上的异质成核现象。二水草酸钙主要通过平行孪晶生长。穿插孪晶较为罕见。无定形二水草酸钙向自形（完全由相互成固定角度的平整面界定）二水草酸钙的转变是通过平行裂隙，随后晶体像砖墙一样堆叠实现的，而水草酸钙的自形转变是通过双锥体从无定形晶体表面突出实现的。偶尔也会发现晶体溶解的迹象。虽然晶体的聚集被认为在结石核心形成中起关键作用，但已形成晶体的尺寸增长以及孪晶和外延晶体共生显然在梗阻性尿路结石形成中起重要作用。
